Why Extreme Rains Are Gaining Strength As The Climate Warms

[bluewave]

https://www.nature.com/articles/d41586-018-07447-1

NEWS FEATURE 

20 NOVEMBER 2018

Why extreme rains are gaining strength as the climate warms

 

From Atlantic hurricanes to the Indian monsoons, storms are getting worse and becoming more erratic.

 

The downpour began on 13 September, when the centre of Hurricane Florence was still hundreds of kilometres from North Carolina’s coast. As the giant storm lurched towards land, officials ordered more than 1.5 million people to evacuate, warning of “life-threatening” damage. On 15 September, Florence finally crashed into the United States, where it slowed to a crawl and unleashed even heavier rains. In some places, the deluge continued non-stop for four days.

By the time it was all over, Florence had dumped record amounts of rain — including nearly one metre in the town of Elizabethtown, North Carolina — and caused catastrophic flooding. Dozens of people died, and the storm racked up tens of billions of dollars in damages. Even now, months later, the area is struggling to recover.

The story of how Florence brought a thriving region to its knees is about to get a lot more familiar. Climate scientists expect that as global temperatures rise, much more rain will fall in extreme storms. The warmer the atmosphere, the more moisture it can hold, which means storms can get wetter. Even before Florence made landfall, a team based at Stony Brook University in New York predicted that the hurricane’s heaviest rains would dump at least 50% more precipitation than would have happened people not warmed the planet.

Extreme rains — along with the flooding, landslides and other devastation they cause — are some of the deadliest weather events worldwide. This year, heavy rains in the Indian state of Kerala killed more than 470 people, and flooding in southwestern Japan left more than 200 dead. In the United States, flooding, severe storms and tropical cyclones account for 9 of the 11 natural disasters that have topped US$1 billion in damages so far this year. But forecasting how the most punishing rains might change in the future has been notoriously difficult, because scientists can’t easily simulate these storms in computer models.

Now, many research teams are making advances in understanding the future of extreme precipitation across the world, thanks to models with very high resolution that can provide insight into how storms evolve. Some of the most sophisticated forecasts suggest that as the globe warms, more rains will fall in severe, intermittent storms rather than in the kind of gentle soaking showers that can sustain crops. Other research indicates that the ways in which thunderstorms organize themselves could change fundamentally, leading to bigger and more-powerful storms that could mean more flooding.

All that makes Florence, the Indian disaster and other devastating downpours a probable glimpse of the future if greenhouse-gas emissions continue to rise. “The next 20 years will be worse than the last 20 years — all indications point to that,” says Angeline Pendergrass, an atmospheric scientist at the National Center for Atmospheric Research (NCAR) in Boulder, Colorado. “And things will be completely nuts by the end of the century if we keep doing what we’re doing now.”

More moisture

In Kerala, it all started with a wet June and July, and accelerated over the following month. The first 20 days of August brought 164% more rain than usual. Throughout the state, landslides swept into towns and buildings as sodden ground collapsed. More than 1 million people fled their homes.

The weather might not have been the only problem in this case. Some have criticized local officials for not better managing the build-up of water behind local dams. But the flooding was ultimately traced back to heavier-than-usual storms during the summer monsoon.

And it’s clear that such storms are carrying more moisture than they used to. The moisture in the air changes depending on temperature: heat that air by 1 °C, and it can hold approximately 7% more water. The Intergovernmental Panel on Climate Change has concluded that many parts of the world are already seeing increases in heavy precipitation, thanks to human-induced climate change.

“It’s just basic physics,” says Kenneth Kunkel, an atmospheric scientist at North Carolina State University in Asheville. “Big storms with large amounts of rainfall are limited by the amount of water vapour in the atmosphere. As we increase water vapour in the atmosphere, we can increase the amount of rainfall in these extreme precipitation events.”

But the precipitation story turns out to be more complicated than that. A thunderstorm is essentially a tower of upward-moving winds that feed themselves by sucking in warm air from nearby. When the air rises high enough, it cools and condenses into rain. Storms can generate their own weather, such as creating cold pools of air near the ground that trigger more convection. And climate change can amplify these effects, causing updrafts to grow stronger and wider, which pulls in more warm air from surrounding regions and leads to more rain. 

This apparently happened in Hurricane Harvey — the rainiest storm in US history, which drowned much of Houston and south Texas in a $125-billion disaster in August last year. Three separate studies have concluded that Harvey’s heaviest rains could not be explained simply by the increase of water vapour in the atmosphere1–3. Climate change made it even wetter than that. 

At NCAR, Pendergrass is working with global climate models to pin down what this might mean for extreme events in the future — and especially, where they might occur. She analyses how climate change is altering how heat and energy flow in the atmosphere, which changes how precipitation is spread around the globe.

Last year, she and her colleagues reported on three computer simulations showing that precipitation is likely to become more variable across almost all land areas if temperatures rise through the rest of the century4. In other words, weather will get crazier: wet periods will give way to dry periods more erratically, and vice versa, across nearly all the continents.

Now, she has drilled down to study the unevenness of precipitation — that is, the difference between a light drizzle and a torrential downpour. She and Reto Knutti, an atmospheric scientist at the Swiss Federal Institute of Technology in Zurich (ETH Zurich) in Switzerland, analysed global rainfall records between 1999 and 2014. For the median of all locations in the study, it took only 12 days for half of the year’s rain to fall55. “Things that are considered extreme contribute a lot to the total precipitation, more than a lot of my colleagues may realize,” she says.

Looking ahead with a climate model, the researchers found that that this kind of unevenness will increase. If greenhouse-gas emissions continue to climb quickly in the future, half of the extra rainfall will happen during the wettest six days of the year. 

That means more deluges — and the dangers that follow (see ‘Heavy rain’). Pendergrass has been talking with water managers in Denver, Colorado, who want to know how much flooding they need to prepare their dams to handle in the future. She says other areas should prepare, too. “Rather than assuming more rain in general, society needs to take measures to deal with little change most of the time, and a handful of events with much more rain,” she and Knutti wrote last month in Geophysical Research Letters5.

 

Another set of simulations underscores how society needs to prepare for these swings between wet and dry. This work, led by atmospheric scientist Zachary Zobel while he was at the University of Illinois in Urbana–Champaign, took a global climate model that usually calculates conditions every 100 kilometres and forced it to a much higher resolution, of just 12 kilometres. “You need as high a spatial resolution as you can get,” says Zobel, who is now at the Woods Hole Research Center in Falmouth, Massachusetts. At a resolution of 12 kilometres, the model can reveal small-scale phenomena in the atmosphere that are important for simulating storms. But Zobel’s model requires a lot of computing power, so the team looked only at the continental United States, not the entire globe. Even using a supercomputer, it took the better part of a year for the model to crunch through its calculations6. But in the end, the researchers got a detailed look at how different parts of the country would be affected, in both temperature and precipitation extremes, if greenhouse-gas emissions continue to remain high out until 2094.

Boom or bust

The scientists found that extreme precipitation events would increase over most of the country. They also spotted some larger changes in future patterns, such as in the position of the west-to-east jet stream that controls weather over much of the middle part of the United States.

That change arises because the Arctic is currently warming faster than are the mid-latitudes, so there is less of a temperature difference between the two regions. In response, the jet stream shifts northward in the simulations, bringing warm moist air from the Gulf of Mexico behind it. The result is that the midwestern states, where the bulk of the country’s corn and wheat crops are grown, will probably see more severe storms each spring during the planting season. Meanwhile, dry spells will grow longer, the model suggests. 

“It really comes down to a boom-or-bust-type precipitation pattern,” Zobel says. “That will complicate how farmers deal with planting their crops.” The work appeared last month in Earth’s Future6.

For Andreas Prein, the future hit home in 2002, when heavy summer rains drenched central Europe. Prein was serving in the Austrian military, and his unit was dispatched to help flood-ravaged areas of northern Austria, where tiny brooks became torrents and damages reached €3 billion (US$3.4 billion). “It was really shocking to see how little streams could do such devastation,” says Prein. “It was almost unbelievable.”

Today, Prein is an atmospheric scientist at NCAR and a leader in a new type of high-resolution climate modelling. This research aims to simulate future climate in even higher resolution than Zobel’s. Its computations narrow down to scales of four kilometres or less — which is so computationally expensive that it can be done only for relatively small regions.

Four kilometres is crucial because it’s the dimension at which individual storms evolve and grow stronger through convection. The field is known as convection-permitting climate modelling, and it allows researchers to simulate storms much more realistically. The calculations are similar to what weather forecasters do to predict how storms will develop over the next day or two. “But we want to simulate decades to centuries,” Prein says. “It’s basically copying what weather forecasting does, but on much longer time scales.”

In ongoing work, UK-based researchers have been running European-wide climate simulations at 2.2-kilometre resolution and have spotted some warning signs about future storms. “At the moment across most of Europe, the season we get extremes is primarily summer,” says team member Elizabeth Kendon, a climate scientist at the Met Office in Reading, UK. In the simulations of a warmer world, summer downpours get heavier, and extreme events occur later in the year. That suggests officials might need to do more to prepare for flooding from winter storms.

Hurricanes are another major concern. Christina Patricola and Michael Wehner, at the Lawrence Berkeley National Laboratory in California, have used convection-permitting models to study the devastating hurricanes of Katrina in 2005 and Irma and Maria in 2017. They found that climate change had boosted rains within these storms by up to 9% — and that future warming would almost certainly mean more extreme rainfall from similar hurricanes7.

One of the biggest convection-permitting simulations so far, run by NCAR, covered the continental United States at a resolution of four kilometres8. It was actually a pair of simulations, one looking back and another peering forward. The first one simulated global climate between October 2000 and September 2013 to test how accurately the model could reproduce what happened during those years. “We started as you would start a weather forecast, and then we just didn’t stop for 13 years,” says Prein. 

The second simulation looked at a similar period at the end of the century, incorporating factors that would be expected if society continues to produce greenhouse gases at a high rate. 

By comparing the two, the scientists could tease out the probable effects of increasing greenhouse-gas levels. And because the simulations were at such high resolution, they could capture how individual storms are likely to form and evolve in the future.

Among the many findings of such models are that intense US thunderstorms will more than triple in frequency by the end of the century, and their maximum rainfall will increase by 15–40%9. The storms will also grow larger, almost doubling the area that would get hit with heavy rainfall. That has big implications for flood risks. “If you think about a large thunderstorm moving over a city area, it makes a big difference if the storm covers half the city catchment or all of it,” says Prein.

He and his colleagues at NCAR are now developing a second set of simulations which they hope to begin running in the coming months. It will extend the simulations northwards into Canada, aiming to study whether the powerful thunderstorms that regularly rip through the upper midwest of the United States will move into Canada in the future. The work will also cover periods lasting 20 years rather than 13, which the scientists hope will enable them to capture longer trends in changing weather patterns. 

Whatever is on the way, it will almost certainly be hard to miss. Sitting in her office at NCAR on a sun-drenched morning, Pendergrass pulls up a figure showing computer simulations of what kinds of extreme precipitation might lurk in the future. “What we have seen so far is incredibly small compared to what’s coming,” she says. “And that’s kind of terrifying.” 

Nature 563, 458-460 (2018)

doi: 10.1038/d41586-018-07447-1

 

 

[etudiant]

Seen that the world has warmed close to a degree Centigrade since the 1880s, there should be solid evidence in the global weather records documenting this effect of increasing warmth.

Have there been any papers published that quantify the change?

[snowlover91]

So how do we distinguish between normal weather extremes and those supposedly caused by AGW? It seems to me that every event that is out of the ordinary is automatically blamed on AGW rather than looking objectively to see if it’s within the norm historically or if natural processes are responsible. A major hurricane makes landfall and automatically AGW is to blame. Drought or flooding? Yep it has to be because of AGW. Wildfires or severe thunderstorms hit an area hard.. yep you guessed it, AGW. It’s so ridiculous that we’ve reached a point where any weather event is automatically labeled as a side effect of AGW. 

Here’s some info on extreme events with hard scientific data to support it, not computer model simulations and predictions which are unstable and inaccurate. In a random and chaotic atmosphere we see how quickly models lose accuracy, yet somehow we expect models to be accurate years in advance as in the nature study cited? Ok... 

Why are tornadoes near record lows in the US this year? If extreme events are supposed to be more common why are they so low? I guess AGW must be responsible for this (sarcasm)

 

Per this article there has been little to no trend in global precip patterns. https://journals.ametsoc.org/doi/pdf/10.1175/BAMS-D-17-0065.1

"Changes in precipitation patterns are highly related to variability of atmospheric circulations, which can be influenced by a warming climate [e.g., shifts in storm tracks (Trenberth 2011)], leading to an increasing trend in global precipitation (Ren et al. 2013). As possible causes, some suggest an increase in hydrologic extremes (Karl and Knight 1998; Groisman et al. 2005; Alexander et al. 2006; Westra et al. 2013) in response to a warming climate, while others propose location-specific intensification of the global hydrologic cycle, where the wet regions get wetter and the dry regions get drier (Held and Soden 2006). At the same time, there is little evidence provided by historical observations supporting the notion that the wet gets wetter and the dry gets drier (Greveet al. 2014). The take-home message from our study using the new 33+ years [1983-2015] of high-resolution global precipitation dataset is that there seems not to be any detectable and significant positive trends in the amount of global precipitation due to the now well-established increasing global temperature. While there are regional trends, there is no evidence of increase in precipitation at the global scale in response to the observed global warming.”

Heat waves in the US aren't as bad as the 1930s still. Why? What about the 1934 drought and dust bowl? We haven’t seen anything remotely close to that in the US since then.

“For the conterminous United States, the highest number of heat waves occurred in the 1930s, with the fewest in the 1960s. The 2001–10 decade was the second highest but well below the 1930s. Regionally, the western regions (including Alaska) had their highest number of heat waves in the 2000s, while the 1930s were dominant in the rest of the country. Droughts too have multiyear and longer variability. Instrumental data indicate that the Dust Bowl of the 1930s and the 1950s drought were the most widespread twentieth-century droughts in the United States, while tree ring data indicate that the mega droughts over the twelfth century exceeded anything in the twentieth century in both spatial extent and duration.” (Peterson et al., 2013 ) https://journals.ametsoc.org/doi/pdf/10.1175/BAMS-D-12-00066.1

 

NOAA says the following regarding hurricane activity...

"While there have been increases in U.S. landfalling hurricanes and basin-wide hurricane counts since the since the early 1970s, Figure 4 shows that these recent increases are not representative of the behavior seen in the century long records. In short, the historical Atlantic hurricane record does not provide compelling evidence for a substantial greenhouse warming-induced long-term increase." 

 

Klotzbach has this image and a great discussion. Worth a read.

"Despite a lack of trend in observed CONUS landfalling hurricane activity since 1900, large increases in inflation-adjusted hurricane-related damage have been observed, especially since the middle part of the twentieth century. We demonstrate that this increase in damage is strongly due to societal factors, namely, increases in population and wealth along the U.S. Gulf and East Coasts." https://journals.ametsoc.org/doi/10.1175/BAMS-D-17-0184.1

 

Here's another look at US temperatures by Judith Curry using USHCN data. It was hotter in the past than today.  https://judithcurry.com/2016/12/16/on-the-decrease-of-hot-days-in-the-us/

 

What's my point? It's easy for AGW alarmists like yourself to make things sound like the world is ending but conveniently ignore other variables that are necessary for a scientific discussion. Why not talk about the decrease in tornadoes, the decrease in 100+ days in the US, no change globally in precious trends based on quantifiable data (not model simulations) or the decrease in major landfalling continental US hurricanes? A fair and scientific discussion looks at both sides and follows the evidence wherever it may lead. 

[snowlover91]

3 hours ago, etudiant said:

Seen that the world has warmed close to a degree Centigrade since the 1880s, there should be solid evidence in the global weather records documenting this effect of increasing warmth.

Have there been any papers published that quantify the change?

See this study as one example. 

Per this article there has been little to no trend in global precip patterns. https://journals.ametsoc.org/doi/pdf/10.1175/BAMS-D-17-0065.1

"Changes in precipitation patterns are highly related to variability of atmospheric circulations, which can be influenced by a warming climate [e.g., shifts in storm tracks (Trenberth 2011)], leading to an increasing trend in global precipitation (Ren et al. 2013). As possible causes, some suggest an increase in hydrologic extremes (Karl and Knight 1998; Groisman et al. 2005; Alexander et al. 2006; Westra et al. 2013) in response to a warming climate, while others propose location-specific intensification of the global hydrologic cycle, where the wet regions get wetter and the dry regions get drier (Held and Soden 2006). At the same time, there is little evidence provided by historical observations supporting the notion that the wet gets wetter and the dry gets drier (Greveet al. 2014). The take-home message from our study using the new 33+ years [1983-2015] of high-resolution global precipitation dataset is that there seems not to be any detectable and significant positive trends in the amount of global precipitation due to the now well-established increasing global temperature. While there are regional trends, there is no evidence of increase in precipitation at the global scale in response to the observed global warming.”

[snowlover91]

Not to mention even the IPCC recognizes no OBSERVABLE trends in various areas. 

IPCC AR5, Chapter 2:

1. “Current datasets indicate no significant observed trends in global tropical cyclone frequency over the past century”
2. “No robust trends in annual numbers of tropical storms, hurricanes and major hurricanes counts have been identified over the past 100 years”
3. “In summary, there continues to be a lack of evidence and thus low confidence regarding the sign of trend in the magnitude and/or frequency of floods on a global scale”
4. “The statement about the absence of trends in impacts attributable to natural or anthropogenic climate change holds for tropical and extratropical storms and tornados”
5. “In summary, there is low confidence in observed trends in small-scale severe weather phenomena such as hail and thunderstorms”
6. “In summary, the current assessment concludes that there is not enough evidence at present to suggest more than low confidence in a global-scale observed trend in drought or dryness (lack of rainfall) since the middle of the 20th century.”
7. “In summary, confidence in large scale changes in the intensity of extreme extratropical cyclones since 1900 is low”

 

Here is what the IPCC had to say about precip trends in AR5. 

AR4 concluded that precipitation has generally increased over land north of 30°N over the period 1900–2005 but downward trends dominate the tropics since the 1970s. AR4 included analysis of both the GHCN (Vose et al., 1992) and CRU (Mitchell and Jones, 2005) gauge-based precipitation datasets for the globally averaged annual precipitation over land. For both datasets the overall linear trend from 1900 to 2005 (1901– 2002 for CRU) was positive but not statistically significant (Table 3.4 from AR4). Other periods covered in AR4 (1951–2005 and 1979–2005) showed a mix of negative and positive trends depending on the dataset.

Since AR4, existing datasets have been updated and a new dataset developed. Figure 2.28 shows the century- scale variations and trends on globally and zonally averaged annual precipitation using five datasets: GHCN V2 (updated through 2011; Vose et al., 1992), Global Precipitation Climatology Project V2.2 (GPCP) combined raingauge-satellite product (Adler et al., 2003), CRU TS 3.10.01 (updated from Mitchell and Jones, 2005), Global Precipitation Climatology Centre V6 (GPCC) dataset (Becker et al., 2013) and a reconstructed dataset by Smith et al. (2012). Each data product incorporates a different number of station series for each region. The Smith et al. product is a statistical reconstruction using Empirical Orthogonal Functions, similar to the NCDC MLOST global temperature product (Section 2.4.3) that does provide coverage for most of the global surface area although only land is included here. The datasets based on in situ observations only start in 1901, but the Smith et al. dataset ends in 2008, while the other 3 datasets contain data until 2010.

For the longest common period of record (1901-2008) the GHCN and GPCC datasets show statistically significant but opposite trends in globally averaged precipitation, with the Smith et al. and CRU datasets showing small non-significant declines (Table 2.9). Global trends for the shorter period (1951–2008) also show a mix of statistically non-significant positive and negative trends amongst the three datasets. These differences among datasets, particularly for the early part of the 20th century indicate that long-term increases in global precipitation discussed in AR4 are uncertain, owing to issues in data coverage in the early part of the 20th century (Wan et al., 2013).

   In summary, confidence in precipitation change averaged over global land areas is low prior to 1950 and medium afterwards because of insufficient data, particularly in the earlier part of the record. Available globally incomplete records show mixed and nonsignificant long-term trends in reported global mean changes. Further, when virtually all the land area is filled in using a reconstruction method, the resulting time series shows little change in land-based precipitation since 1900.

[snowlover91]

Climate models being used to forecast future rainfall trends are a joke btw. Judith curry wrote this “The climate models simply are not fit for this task. Such analyses implicitly assume the a) climate model sensitivity is correct; b) climate models correctly simulate internal variability; c) climate models correctly simulate extreme events; d) climate models correctly simulate thermodynamic feedbacks; e) climate models correctly simulate large-scale weather events and blocking patterns.” https://judithcurry.com/2018/09/18/hurricane-florence-climate-dynamics-context/

[LibertyBell]

What about anomalous record breaking blocking that has been happening the last few years causing weird storm tracks and much slower moving storms?

[snowlover91]

3 hours ago, LibertyBell said:

What about anomalous record breaking blocking that has been happening the last few years causing weird storm tracks and much slower moving storms?

 

Some of that is addressed in the article l linked above by Judith Curry. Well worth the read. 

[bluewave]

9 hours ago, etudiant said:

Seen that the world has warmed close to a degree Centigrade since the 1880s, there should be solid evidence in the global weather records documenting this effect of increasing warmth.

Have there been any papers published that quantify the change?

I have posted numerous papers here in the past on the increasing record rains in the US. But this is the first paper to run the high resolution models for the future to show how and where the increases will continue.

http://www.climatesignals.org/climate-signals/extreme-precipitation-increase

• According to the US Fourth National Climate Assessment, "Heavy precipitation events [defined as the heaviest 1 percent of all daily events] in most parts of the United States have increased in both intensity and frequency since 1901."[7]
• From 1958 to 2012, the amount of precipitation falling in very heavy events increased by 71 percent in the Northeast, 27 percent in the Southeast, 37 percent in the Midwest, 16 percent in the Great Plains, 5 percent in the Southwest, and 12 percent in the Northwest.[8]
• Over the period from 1994-2008, extreme precipitation events linked to hurricanes accounted for 32 percent of extreme precipitation increases in the Northeast, 51 percent in the Central US, 48 percent in the South, and 100 percent in the Southeast (for regions, see here).[9]
• The heaviest rainfall events have become more frequent across most of the country, and projects that heavy precipitation events that historically occurred once in 20 years will occur as frequently as every 5 to 15 years by late this century.[8]
• In the past century, the US has witnessed a 20 percent increase in the amount of precipitation falling in the heaviest downpours.[10]

http://www.nws.noaa.gov/oh/hdsc/aep_storm_analysis/

 

HDSC analyzes annual exceedance probabilities (AEPs) for selected significant storm events for which observed precipitation amounts for at least one duration have AEP of 1/500 or less over a large area.

AEP maps have been created for the events listed below for selected durations that show the lowest exceedance probabilities for the largest area. For most recent events, associated shapefiles can be downloaded using the links provided in the table. Because the beginning of the observation period for a selected duration is not identical across the area, the AEP map does not characterize isohyets at any particular point in time, but rather within the whole event. For some events, the maximum observed precipitation amounts were also compared with corresponding frequency estimates across a range of durations at central gauged location(s).

Event

AEP map duration(s)

Shapefile

Hurricane Florence, 13-18 September 2018	72-hour	link
Michigan and Wisconsin, 14-18 June 2018	6-hour, 24-hour, 72-hour	link
Ellicott City, Maryland, 27 May 2018	3-hour
Hurricane Maria, 20 September 2017	12-hour	link
Hurricane Harvey, 25-31 August 2017	4-day
Missouri, 28 April - 2 May 2017	48-hour	link
Hurricane Matthew, 6-10 October 2016	12-hour	link
Louisiana, 11-13 August 2016	48-hour
Ellicott City, Maryland, 30 July 2016	3-hour
Northern Wisconsin, 11-12 July 2016	6-hour
West Virginia, 23-24 June 2016	24-hour
Lower Mississippi River Valley, 8-12 March 2016	48-hour
Corsicana, Texas, 24-25 October 2015	24-hour
Austin, Texas, 30 October 2015	3-hour, 6-hour
South Carolina, 2 - 4 October 2015	24-hour, 72-hour
Central Texas, 23-24 May 2015	3-hour, 6-hour
Oklahoma, April - June 2015	20-day,30-day, 60-day
Phoenix, Arizona, 19 August 2014	12-hour
Islip, New York, 13 August 2014	3-hour
Pensacola, Florida, 29-30 April 2014	6-hour
New Mexico, 9-16 September 2013	7-day
Colorado, 9-16 September 2013	24-hour, 48-hour, 7-day
Southern Missouri, 29 July - 8 August 2013	10-day
San Antonio, Texas, 25 May 2013	6-hour
Oklahoma City region, 31 May-1 June 2013	4-hour, 6-hour
Tropical storm Debby, 24-27 June 2012	48-hour
Duluth, Minnesota, 19-20 June 2012	24-hour
Tennessee, 1-2 May 2010	48-hour
Southeastern New England, March 2010	20-day

 

 

[etudiant]

Thank you, bluewave and snowlover91, for a very informative exchange.

Wishing both of you and all the fellow weather lovers on this site a very happy Thanksgiving. We all have much to be thankful for.

[snowlover91]

24 minutes ago, bluewave said:

I have posted numerous papers here in the past on the increasing record rains in the US. But this is the first paper to run the high resolution models for the future to show how and where the increases will continue.

http://www.climatesignals.org/climate-signals/extreme-precipitation-increase

• According to the US Fourth National Climate Assessment, "Heavy precipitation events [defined as the heaviest 1 percent of all daily events] in most parts of the United States have increased in both intensity and frequency since 1901."[7]
• From 1958 to 2012, the amount of precipitation falling in very heavy events increased by 71 percent in the Northeast, 27 percent in the Southeast, 37 percent in the Midwest, 16 percent in the Great Plains, 5 percent in the Southwest, and 12 percent in the Northwest.[8]
• Over the period from 1994-2008, extreme precipitation events linked to hurricanes accounted for 32 percent of extreme precipitation increases in the Northeast, 51 percent in the Central US, 48 percent in the South, and 100 percent in the Southeast (for regions, see here).[9]
• The heaviest rainfall events have become more frequent across most of the country, and projects that heavy precipitation events that historically occurred once in 20 years will occur as frequently as every 5 to 15 years by late this century.[8]
• In the past century, the US has witnessed a 20 percent increase in the amount of precipitation falling in the heaviest downpours.[10]

 

 

 

Meanwhile the global signal exhibits no statistically significant change. Weather patterns shift and change with time. What happens regionally is NOT representative of a global change and does not prove global warming is the cause for any regional changes either. Natural variability and random natural processes can account for both extreme events as well as increases or decreases over time in precip patterns. See below for more info. Happy Thanksgiving!

“The aim of this study is to examine the contribution of North Atlantic tropical cyclones (TCs) to flooding and heavy rainfall across the continental United States. Analyses highlight the spatial variability in these hazards, their temporal changes in terms of frequency and magnitude, and their connection to large-scale climate, in particular to the North Atlantic Oscillation (NAO) and El Niño-Southern Oscillation (ENSO). We use long-term stream and rain gage measurements, and our analyses are based on annual maxima (AMs) and peaks-over-threshold (POTs). TCs contribute to ∼20–30% of AMs and POTs over Florida and coastal areas of the eastern United States, and the contribution decreases as we move inland. We do not detect statistically significant trends in the magnitude or frequency of TC floods. Regarding the role of climate, NAO and ENSO do not play a large role in controlling the frequency and magnitude of TC flooding. The connection between heavy rainfall and TCs is comparable to what observed in terms of flooding. Unlike flooding, NAO plays a significant role in TC-related extreme rainfall along the U.S. East Coast, while ENSO is most strongly linked to the TC precipitation in Texas.”

https://www.sciencedirect.com/science/article/pii/S0022169418301549

“Analysis of the seasonality in heavy daily precipitation trends supports physical arguments that their changes during 1979–2013 have been intimately linked to internal decadal ocean variability and less so to human-induced climate change. Most of the southern U.S. decrease has occurred during the cold season that has been dynamically driven by an atmospheric circulation reminiscent of teleconnections linked to cold tropical eastern Pacific SSTs. Most of the northeastern U.S. increase has been a warm season phenomenon, the immediate cause for which remains unresolved.” https://journals.ametsoc.org/doi/full/10.1175/JCLI-D-15-0441.1

 

Extreme event attribution, when done in a scientifically and intellectually honest way, follows these general rules: 

“A very long time series of historical observations of the extreme event at a particular location (which is rarely available)

An understanding of the variability of extreme weather events associated with multi-decadal ocean oscillations (which requires at least a century of observations)

Climate models that accurately simulate both natural internal variability on timescales of years to centuries and the extreme weather events (a pipe dream; we are not even close)”

Read here for more. https://judithcurry.com/2016/03/14/attribution-of-extreme-weather-events/

[bluewave]

12 minutes ago, snowlover91 said:

Meanwhile the global signal exhibits no statistically significant change. Weather patterns shift and change with time. What happens regionally is NOT representative of a global change and does not prove global warming is the cause for any regional changes either. Natural variability and random natural processes can account for both extreme events as well as increases or decreases over time in precip patterns. See below for more info. Happy Thanksgiving!

“The aim of this study is to examine the contribution of North Atlantic tropical cyclones (TCs) to flooding and heavy rainfall across the continental United States. Analyses highlight the spatial variability in these hazards, their temporal changes in terms of frequency and magnitude, and their connection to large-scale climate, in particular to the North Atlantic Oscillation (NAO) and El Niño-Southern Oscillation (ENSO). We use long-term stream and rain gage measurements, and our analyses are based on annual maxima (AMs) and peaks-over-threshold (POTs). TCs contribute to ∼20–30% of AMs and POTs over Florida and coastal areas of the eastern United States, and the contribution decreases as we move inland. We do not detect statistically significant trends in the magnitude or frequency of TC floods. Regarding the role of climate, NAO and ENSO do not play a large role in controlling the frequency and magnitude of TC flooding. The connection between heavy rainfall and TCs is comparable to what observed in terms of flooding. Unlike flooding, NAO plays a significant role in TC-related extreme rainfall along the U.S. East Coast, while ENSO is most strongly linked to the TC precipitation in Texas.”

https://www.sciencedirect.com/science/article/pii/S0022169418301549

“Analysis of the seasonality in heavy daily precipitation trends supports physical arguments that their changes during 1979–2013 have been intimately linked to internal decadal ocean variability and less so to human-induced climate change. Most of the southern U.S. decrease has occurred during the cold season that has been dynamically driven by an atmospheric circulation reminiscent of teleconnections linked to cold tropical eastern Pacific SSTs. Most of the northeastern U.S. increase has been a warm season phenomenon, the immediate cause for which remains unresolved.” https://journals.ametsoc.org/doi/full/10.1175/JCLI-D-15-0441.1

 

Extreme event attribution, when done in a scientifically and intellectually honest way, follows these general rules: 

“A very long time series of historical observations of the extreme event at a particular location (which is rarely available)

An understanding of the variability of extreme weather events associated with multi-decadal ocean oscillations (which requires at least a century of observations)

Climate models that accurately simulate both natural internal variability on timescales of years to centuries and the extreme weather events (a pipe dream; we are not even close)”

Read here for more. https://judithcurry.com/2016/03/14/attribution-of-extreme-weather-events/

It's not surprising that you link to someone who is well known to downplay anything having to do with climate change. We saw in 2013 how this type of mindset can lead theories about the climate that are incorrect. Remember back in 2013 when she published that there would be no further global warming through the 2030's?

https://judithcurry.com/2013/10/10/the-stadium-wave/

“The stadium wave signal predicts that the current pause in global warming could extend into the 2030s,” Wyatt said, the paper’s lead author.

Curry added, “This prediction is in contrast to the recently released IPCC AR5 Report that projects an imminent resumption of the warming, likely to be in the range of a 0.3 to 0.7 degree Celsius rise in global mean surface temperature from 2016 to 2035.” Curry is the chair of the Department of Earth and Atmospheric Sciences at the Georgia Institute of Technology.

[snowlover91]

52 minutes ago, bluewave said:

It's not surprising that you link to someone who is well known to downplay anything having to do with climate change. We saw in 2013 how this type of mindset can lead theories about the climate that are incorrect. Remember back in 2013 when she published that there would be no further global warming through the 2030's?

https://judithcurry.com/2013/10/10/the-stadium-wave/

“The stadium wave signal predicts that the current pause in global warming could extend into the 2030s,” Wyatt said, the paper’s lead author.

Curry added, “This prediction is in contrast to the recently released IPCC AR5 Report that projects an imminent resumption of the warming, likely to be in the range of a 0.3 to 0.7 degree Celsius rise in global mean surface temperature from 2016 to 2035.” Curry is the chair of the Department of Earth and Atmospheric Sciences at the Georgia Institute of Technology.

 

I also remember the various AGW scientists who said we would be ice free by now and yet we aren’t among many other AGW failed predictions. My point from the article I linked is a valid one; attribution of extreme events requires long term and reliable observational evidence, understanding of the natural cycles in play and how they affect precip patterns and climate models which can properly understand climate feedbacks and other mechanisms. Read the other papers I posted which link US changes to natural variability due to various mechanisms and globally show no statistically significant trend.

The IPCC even agrees that there is no statistically significant precip trend globally. Here it is in case you missed it earlier:

“In summary, confidence in precipitation change averaged over global land areas is low prior to 1950 and medium afterwards because of insufficient data, particularly in the earlier part of the record. Available globally incomplete records show mixed and nonsignificant long-term trends in reported global mean changes. Further, when virtually all the land area is filled in using a reconstruction method, the resulting time series shows little change in land-based precipitation since 1900.”

[bluewave]

59 minutes ago, snowlover91 said:

 

I also remember the various AGW scientists who said we would be ice free by now and yet we aren’t among many other AGW failed predictions. My point from the article I linked is a valid one; attribution of extreme events requires long term and reliable observational evidence, understanding of the natural cycles in play and how they affect precip patterns and climate models which can properly understand climate feedbacks and other mechanisms. Read the other papers I posted which link US changes to natural variability due to various mechanisms and globally show no statistically significant trend.

The IPCC even agrees that there is no statistically significant precip trend globally. Here it is in case you missed it earlier:

“In summary, confidence in precipitation change averaged over global land areas is low prior to 1950 and medium afterwards because of insufficient data, particularly in the earlier part of the record. Available globally incomplete records show mixed and nonsignificant long-term trends in reported global mean changes. Further, when virtually all the land area is filled in using a reconstruction method, the resulting time series shows little change in land-based precipitation since 1900.”

You realize that that has been updated in recent years with the long list of studies that I posted and linked to. As for the Arctic sea ice predictions, the sea ice fell much faster than many models forecast since the late 1990's. Excellent sources like the NSIDC never forecast ice free conditions during this decade. They actually cautioned against that kind of view.

[snowlover91]

35 minutes ago, bluewave said:

You realize that that has been updated in recent years with the long list of studies that I posted and linked to. As for the arctic sea ice predictions, the sea ice fell much faster than many models forecast since the late 1990's. Excellent sources like the NSIDC never forecast ice free conditions during this decade. 

As I cited there are other studies which indicate there is no statistically significant trend in precipitation and address studies like the one you linked. The IPCC AR5 report also made it quite clear there was no trend either.  

Many of the articles cited in your link simply look only at regional changes and make conclusions that assume AGW is to blame. Others use climate models in an attempt to compare observational data with model simulations and conclude that it can’t be natural causes for any regional/local changes. The problem with that is they’re assuming the climate models are handling the changes at local, regional and global levels PERFECTLY without any error and that any feedbacks and other mechanisms are perfectly modeled too. We know how poorly computer models handle our own weather forecasting 5+ days out and yet somehow people like yourself expect climate models to be reliable for simulating internal variability when in fact they are pretty bad at it. I prefer relying on observational data over computer modeling which per the study below indicates no statistically significant changes.  

https://journals.ametsoc.org/doi/pdf/10.1175/BAMS-D-17-0065.1

"Changes in precipitation patterns are highly related to variability of atmospheric circulations, which can be influenced by a warming climate [e.g., shifts in storm tracks (Trenberth 2011)], leading to an increasing trend in global precipitation (Ren et al. 2013). As possible causes, some suggest an increase in hydrologic extremes (Karl and Knight 1998; Groisman et al. 2005; Alexander et al. 2006; Westra et al. 2013) in response to a warming climate, while others propose location-specific intensification of the global hydrologic cycle, where the wet regions get wetter and the dry regions get drier (Held and Soden 2006). At the same time, there is little evidence provided by historical observations supporting the notion that the wet gets wetter and the dry gets drier (Greveet al. 2014). The take-home message from our study using the new 33+ years [1983-2015] of high-resolution global precipitation dataset is that there seems not to be any detectable and significant positive trends in the amount of global precipitation due to the now well-established increasing global temperature. While there are regional trends, there is no evidence of increase in precipitation at the global scale in response to the observed global warming.”

Arctic sea ice predictions have been wrong for a long time. Hansen and Jay Zwally are two for example who have been wrong. The news media has been predicting an ice free arctic since the 1930s and it still hasn’t happened despite the hype and outlandish claims. While the NSIDC hasn’t made any predictions there are plenty of scientists and supposed experts hyping the ice free by xx year that simply hasn’t happened. 

[bluewave]

19 minutes ago, snowlover91 said:

And as I cited there are other studies which indicate there is no statistically significant trend in precipitation and address studies like the one you linked. 

Per this study based on observational evidence there has been little to no trend in global precip patterns. https://journals.ametsoc.org/doi/pdf/10.1175/BAMS-D-17-0065.1

"Changes in precipitation patterns are highly related to variability of atmospheric circulations, which can be influenced by a warming climate [e.g., shifts in storm tracks (Trenberth 2011)], leading to an increasing trend in global precipitation (Ren et al. 2013). As possible causes, some suggest an increase in hydrologic extremes (Karl and Knight 1998; Groisman et al. 2005; Alexander et al. 2006; Westra et al. 2013) in response to a warming climate, while others propose location-specific intensification of the global hydrologic cycle, where the wet regions get wetter and the dry regions get drier (Held and Soden 2006). At the same time, there is little evidence provided by historical observations supporting the notion that the wet gets wetter and the dry gets drier (Greveet al. 2014). The take-home message from our study using the new 33+ years [1983-2015] of high-resolution global precipitation dataset is that there seems not to be any detectable and significant positive trends in the amount of global precipitation due to the now well-established increasing global temperature. While there are regional trends, there is no evidence of increase in precipitation at the global scale in response to the observed global warming.”

Arctic sea ice predictions have been wrong for a long time. Hansen and Jay Zwally are two for example who have been wrong. The news media has been predicting an ice free arctic since the 1930s and it still hasn’t happened despite the hype and outlandish claims. While the NSIDC hasn’t made any predictions there are plenty of scientists and supposed experts hyping the ice free by xx year that simply hasn’t happened. 

The beauty of science is that it continuously updates its understanding of climate change based on newer information and technology. Don't worry...the ice free Arctic summer is coming as long as the planet continues to warm through the +1.5C to 2.0 C range. 

[bdgwx]

2 hours ago, snowlover91 said:

I also remember the various AGW scientists who said we would be ice free by now and yet we aren’t among many other AGW failed predictions.

Sure there are aggressive predictions of sea ice loss (Maslowski for example), but these are generally ignored by the majority of experts. They have not been incorporated by the consensus. 

The consensus prediction is currently sitting at around 2050'ish which has actually come down some from the 1990's. So far the consensus has generally underestimated the decline so 2050 may not be aggressive enough. It'll be interesting to see what the IPCC says when AR6 is released in a couple of years.

As a general rule you can find onesie-twosie lines of evidence to support just about any prediction no matter how absurd. That doesn't mean that we should take them seriously or that they should automatically get incorporated into and as the consensus prediction. That's a good thing because if we just blindly accepted every line of evidence we came across then we'd be forced into the awkward and contradictory position of believing that an ice-age and a Permian-like hothouse Earth are both imminent. 

[snowlover91]

33 minutes ago, bluewave said:

The beauty of science is that it continuously updates its understanding of climate change based on newer information and technology. Don't worry...the ice free Arctic summer is coming as long as the planet continues to warm through the +1.5C to 2.0 C range. 

Yep and that’s this this article from April 2018 shows that global precip has demonstrated no changes. I’m not worried seeing as ice extent is the second highest it’s been since 2005 and rapidly increasing still. Happy Thanksgiving!

https://journals.ametsoc.org/doi/abs/10.1175/BAMS-D-17-0065.1

[ORH_wxman]

Seems like you are talking past each other a bit. Model projections versus the empirical historical trends. 

[snowlover91]

16 minutes ago, bdgwx said:

Sure there are aggressive predictions of sea ice loss (Maslowski for example), but these are generally ignored by the majority of experts. They have not been incorporated by the consensus. 

The consensus prediction is currently sitting at around 2050'ish which has actually come down some from the 1990's. So far the consensus has generally underestimated the decline so 2050 may not be aggressive enough. It'll be interesting to see what the IPCC says when AR6 is released in a couple of years.

As a general rule you can find onesie-twosie lines of evidence to support just about any prediction no matter how absurd. That doesn't mean that we should take them seriously or that they should automatically get incorporated into the consensus. That's a good thing because if we just blindly accepted every line of evidence we came across then we'd be forced into the awkward and contradictory position of believing that an ice-age and a Permian-like hothouse Earth are both imminent. 

I agree with you that a majority of experts have delayed predictions, but what the public hears are the sensational claims by a few scientists that are widely publicized by the news media and then don’t verify. Most of them aren’t going to research/study to see what other scientists say or only read news headlines. When those end up being wrong the public loses trust in the global warming theory and is a big reason why many are so skeptical imo. 

I think the big takeaway is that observational data indicates that global precip has demonstrated no statistically significant trend. Looking at observed data and comparing it with climate model simulations and making conclusions, as many studies do, is not a valid methodology in my book because of the inherent flaws in climate models. Observational data of other areas like hurricanes, TC frequency, etc also have not seen any upward trend and if anything a downward one per studies I cited previously. I’m just not seeing any weather extremes out there that can be convincingly linked to the AGW view of things like bluewave continues to assert. 

[snowlover91]

3 minutes ago, ORH_wxman said:

Seems like you are talking past each other a bit. Model projections versus the empirical historical trends. 

I agree. Historical trends and observations are more reliable methods than climate modeling which in a chaotic system like our atmosphere and feedbacks that aren’t all understood is prone to significant errors. 

[snowlover91]

Have a Happy Thanksgiving everyone and enjoy the time with friends and family! 

[bluewave]

15 minutes ago, snowlover91 said:

Yep and that’s this this article from April 2018 shows that global precip has demonstrated no changes. I’m not worried seeing as ice extent is the second highest it’s been since 2005 and rapidly increasing still. Happy Thanksgiving!

https://journals.ametsoc.org/doi/abs/10.1175/BAMS-D-17-0065.1

Again, that doesn't fit with the growing body of recent research that shows otherwise.

https://www.pik-potsdam.de/news/press-releases/record-breaking-heavy-rainfall-events-increased-under-global-warming

Record-breaking heavy rainfall events increased under global warming   07/08/2015 - Heavy rainfall events setting ever new records have been increasing strikingly in the past thirty years. While before 1980, multi-decadal fluctuations inextreme rainfall events are explained by natural variability, a team of scientists of the Potsdam Institute for Climate Impact Research detected a clear upward trend in the past few decades towards more unprecedented daily rainfall events. They find the worldwide increase to be consistent with rising global temperatures which are caused by greenhouse-gas emissions from burning fossil fuels. Short-term torrential rains can lead to high-impact floodings. One out of ten record-breaking rainfall events observed globally in the past thirty years can only be explained if the long-term warming is taken into account. (Photo: Thinkstock) Extreme rainfall in Pakistan 2010 caused devastating flooding which killed hundreds and lead to a cholera outbreak. Other examples of record-breakingprecipitation events in the period studied include rainstorms in Texas in the US, 2010, which caused dozens of flash-floods. And no less than three so-called ‘once-in-a-century’ flooding events in Germany all happened in just a couple of years, starting 1997. “In all of these places, the amount of rain pouring down in one day broke local records – and while each of these individual events has been caused by a number of different factors, we find a clear overall upward trend for these unprecedented hazards”, says lead-author Jascha Lehmann. The average increase is 12 percent globally – but 56 percent in South East Asia An advanced statistical analysis of rainfall data from the years 1901 to 2010 derived from thousands of weather stations around the globe shows that over 1980-2010 there were 12 percent more of these events than expected in a stationary climate, a scenario without global warming. “Due to the upward trend, the worldwide increase of record-breaking daily rainfall events in the very last year of the studied period reaches even 26 percent”, Lehmann adds. The record-breaking anomaly has distinct patterns across Earth’s continents with generally wet regions seeing an over-proportional increase and drier regions less so. In South East Asian countries the observed increase in record-breaking rainfall events is as high as 56 percent, in Europe 31 percent, in the central US 24 percent. In contrast, some regions experienced a significant decrease of record-breaking daily rainfall events. In the Mediterranean, the reduction is 27 percent, and in the Western US 21 percent. Both regions are at risk of severe droughts. The link to climate change: warmer air can hold more water While a statistical analysis of course cannot provide direct physical cause-effect relations, the scientists compared their findings to existing knowledge about how much more water can be stored in the atmosphere when temperatures rise, as given by the well-known Clausius-Clapeyron equation. This additional moisture can be released during short-term heavy rainfall events. The scientists show that the observed increase in unprecedented heavy rainfall events generally fits with this thermodynamically expected increase under global warming. “One out of ten record-breaking rainfall events observed globally in the past thirty years can only be explained if the long-term warming is taken into account,” says co-author Dim Coumou. “For the last year studied, 2010, it is even one event out of four, as the trend is upward”.  Up to now, studies could add up to only medium confidence on how human induced greenhouse gases have contributed to changes in heavy precipitation events at the global and regional scale. The new analysis now helps to fill this research gap. Building on previous work on extreme precipitation, it is the first to study worldwide observational data of record-breaking daily rainfall events in this context. “The recent upward trend is worrying” The scientists took into account that the quality of historic weather data differs from one place to another. For instance, rainfall measurements from the Sahara desert are scarce which inhibits making any conclusions for this particular region. Other regions like Europe or the US are well covered with rainfall measurements stretching back over a century which enables the authors to draw conclusions with high levels of confidence  “The pronounced recent increase in record-breaking rainfall events is of course worrying,” Coumou concludes. “Yet since it is consistent with human-caused global warming, it can also be curbed if greenhouse gas emissions from fossil fuels are substantially reduced.” Article: Lehmann, J., Coumou, D., Frieler, K. (2015): Increased record-breakingprecipitation events under global warming. Climatic Change [DOI: 10.1007/s10584-015-1434-y] Weblink to the article: http://dx.doi.org/10.1007/s10584-015-1434-y

[bdgwx]

23 minutes ago, snowlover91 said:

I agree with you that a majority of experts have delayed predictions, but what the public hears are the sensational claims by a few scientists that are widely publicized by the news media and then don’t verify. Most of them aren’t going to research/study to see what other scientists say or only read news headlines. When those end up being wrong the public loses trust in the global warming theory and is a big reason why many are so skeptical imo. 

There may have been a miscommunication here. The consensus prediction on ice-free Arctic summers has not been delayed. It has actually been expedited. Earlier estimates from the 1990's were 2100 or even later. The IPCC has refined these predictions to be sooner; not later. Many scientists still think the IPCC is underestimating the melt out. Unfortunately, I can't fix the problem of the media (mainly from non-expert bloggers) misrepresenting, exaggerating, or misleading their audience regarding the science of climate change. The best option for those who are serious about learning about climate change or have a vested interest in it should ignore the media and instead listen to what the scientific consensus says. The IPCC publications are actually a pretty good proxy for the consensus IMHO.

[AfewUniversesBelowNormal]

It started in Summer 2016. 

[LibertyBell]

7 hours ago, bdgwx said:

There may have been a miscommunication here. The consensus prediction on ice-free Arctic summers has not been delayed. It has actually been expedited. Earlier estimates from the 1990's were 2100 or even later. The IPCC has refined these predictions to be sooner; not later. Many scientists still think the IPCC is underestimating the melt out. Unfortunately, I can't fix the problem of the media (mainly from non-expert bloggers) misrepresenting, exaggerating, or misleading their audience regarding the science of climate change. The best option for those who are serious about learning about climate change or have a vested interest in it should ignore the media and instead listen to what the scientific consensus says. The IPCC publications are actually a pretty good proxy for the consensus IMHO.

What was this report they recently issued that gave us 12 years before irreversible changes occur?

[bdgwx]

33 minutes ago, LibertyBell said:

What was this report they recently issued that gave us 12 years before irreversible changes occur?

SR15: http://www.ipcc.ch/report/sr15/

The focus was mainly on the 1.5C warming target.

[snowlover91]

8 hours ago, bluewave said:

Again, that doesn't fit with the growing body of recent research that shows otherwise.

https://www.pik-potsdam.de/news/press-releases/record-breaking-heavy-rainfall-events-increased-under-global-warming

Record-breaking heavy rainfall events increased under global warming   07/08/2015 - Heavy rainfall events setting ever new records have been increasing strikingly in the past thirty years. While before 1980, multi-decadal fluctuations inextreme rainfall events are explained by natural variability, a team of scientists of the Potsdam Institute for Climate Impact Research detected a clear upward trend in the past few decades towards more unprecedented daily rainfall events. They find the worldwide increase to be consistent with rising global temperatures which are caused by greenhouse-gas emissions from burning fossil fuels. Short-term torrential rains can lead to high-impact floodings. One out of ten record-breaking rainfall events observed globally in the past thirty years can only be explained if the long-term warming is taken into account. (Photo: Thinkstock) Extreme rainfall in Pakistan 2010 caused devastating flooding which killed hundreds and lead to a cholera outbreak. Other examples of record-breakingprecipitation events in the period studied include rainstorms in Texas in the US, 2010, which caused dozens of flash-floods. And no less than three so-called ‘once-in-a-century’ flooding events in Germany all happened in just a couple of years, starting 1997. “In all of these places, the amount of rain pouring down in one day broke local records – and while each of these individual events has been caused by a number of different factors, we find a clear overall upward trend for these unprecedented hazards”, says lead-author Jascha Lehmann. The average increase is 12 percent globally – but 56 percent in South East Asia An advanced statistical analysis of rainfall data from the years 1901 to 2010 derived from thousands of weather stations around the globe shows that over 1980-2010 there were 12 percent more of these events than expected in a stationary climate, a scenario without global warming. “Due to the upward trend, the worldwide increase of record-breaking daily rainfall events in the very last year of the studied period reaches even 26 percent”, Lehmann adds. The record-breaking anomaly has distinct patterns across Earth’s continents with generally wet regions seeing an over-proportional increase and drier regions less so. In South East Asian countries the observed increase in record-breaking rainfall events is as high as 56 percent, in Europe 31 percent, in the central US 24 percent. In contrast, some regions experienced a significant decrease of record-breaking daily rainfall events. In the Mediterranean, the reduction is 27 percent, and in the Western US 21 percent. Both regions are at risk of severe droughts. The link to climate change: warmer air can hold more water While a statistical analysis of course cannot provide direct physical cause-effect relations, the scientists compared their findings to existing knowledge about how much more water can be stored in the atmosphere when temperatures rise, as given by the well-known Clausius-Clapeyron equation. This additional moisture can be released during short-term heavy rainfall events. The scientists show that the observed increase in unprecedented heavy rainfall events generally fits with this thermodynamically expected increase under global warming. “One out of ten record-breaking rainfall events observed globally in the past thirty years can only be explained if the long-term warming is taken into account,” says co-author Dim Coumou. “For the last year studied, 2010, it is even one event out of four, as the trend is upward”.  Up to now, studies could add up to only medium confidence on how human induced greenhouse gases have contributed to changes in heavy precipitation events at the global and regional scale. The new analysis now helps to fill this research gap. Building on previous work on extreme precipitation, it is the first to study worldwide observational data of record-breaking daily rainfall events in this context. “The recent upward trend is worrying” The scientists took into account that the quality of historic weather data differs from one place to another. For instance, rainfall measurements from the Sahara desert are scarce which inhibits making any conclusions for this particular region. Other regions like Europe or the US are well covered with rainfall measurements stretching back over a century which enables the authors to draw conclusions with high levels of confidence  “The pronounced recent increase in record-breaking rainfall events is of course worrying,” Coumou concludes. “Yet since it is consistent with human-caused global warming, it can also be curbed if greenhouse gas emissions from fossil fuels are substantially reduced.” Article: Lehmann, J., Coumou, D., Frieler, K. (2015): Increased record-breakingprecipitation events under global warming. Climatic Change [DOI: 10.1007/s10584-015-1434-y] Weblink to the article: http://dx.doi.org/10.1007/s10584-015-1434-y

An article from 2015 is more current than the one I posted from 2018 and proves there is a growing consensus on this?  Ok then... 

[chubbs]

A couple of points:

1) Rainfall is only expected to increase by a percent or two per degree of warming on a global basis with some areas becoming drier (mainly dry areas) and others wetter (mainly wet areas) . So difficulty in finding trends in mean precipitation is not surprising.

2) The heaviest precipitation events are expected to increase 7% per degree of warming in line with the ability of the atmosphere to hold moisture. Observations bear this out.

https://www.nature.com/articles/nclimate3110

 

[Save the itchy algae!]

So, wait, warmer air holds more moisture?!? Who would have thought...