New AMS Statement on Climate Change

[PhillipS]

The American Meteorological Society released a new information statement on climate change. [source] It is much stronger in its conclusions than the statement released several years ago. Here are several excerpts:

How is climate changing?

Warming of the climate system now is unequivocal, according to many different kinds of evidence. Observations show increases in globally averaged air and ocean temperatures, as well as widespread melting of snow and ice and rising globally averaged sea level. Surface temperature data for Earth as a whole, including readings over both land and ocean, show an increase of about 0.8°C (1.4°F) over the period 1901─2010 and about 0.5°C (0.9°F) over the period 1979–2010 (the era for which satellite-based temperature data are routinely available). Due to natural variability, not every year is warmer than the preceding year globally. Nevertheless, all of the 10 warmest years in the global temperature records up to 2011 have occurred since 1997, with 2005 and 2010 being the warmest two years in more than a century of global records. The warming trend is greatest in northern high latitudes and over land. In the U.S., most of the observed warming has occurred in the West and in Alaska; for the nation as a whole, there have been twice as many record daily high temperatures as record daily low temperatures in the first decade of the 21st century.

The effects of this warming are especially evident in the planet’s polar regions. Arctic sea ice extent and volume have been decreasing for the past several decades. Both the Greenland and Antarctic ice sheets have lost significant amounts of ice. Most of the world’s glaciers are in retreat.

Other changes, globally and in the U.S., are also occurring at the same time. The amount of rain falling in very heavy precipitation events (the heaviest 1% of all precipitation events) has increased over the last 50 years throughout the U.S. Freezing levels are rising in elevation, with rain occurring more frequently instead of snow at mid-elevations of western mountains. Spring maximum snowpack is decreasing, snowmelt occurs earlier, and the spring runoff that supplies over two-thirds of western U.S. streamflow is reduced. Evidence for warming is also observed in seasonal changes across many areas, including earlier springs, longer frost-free periods, longer growing seasons, and shifts in natural habitats and in migratory patterns of birds and insects.

Why is climate changing?

Climate is always changing. However, many of the observed changes noted above are beyond what can be explained by the natural variability of the climate. It is clear from extensive scientific evidence that the dominant cause of the rapid change in climate of the past half century is human-induced increases in the amount of atmospheric greenhouse gases, including carbon dioxide (CO2), chlorofluorocarbons, methane, and nitrous oxide. The most important of these over the long term is CO2, whose concentration in the atmosphere is rising principally as a result of fossil-fuel combustion and deforestation. While large amounts of CO2 enter and leave the atmosphere through natural processes, these human activities are increasing the total amount in the air and the oceans. Approximately half of the CO2 put into the atmosphere through human activity in the past 250 years has been taken up by the ocean and terrestrial biosphere, with the other half remaining in the atmosphere. Since long-term measurements began in the 1950s, the atmospheric CO2 concentration has been increasing at a rate much faster than at any time in the last 800,000 years. Having been introduced into the atmosphere it will take a thousand years for the majority of the added atmospheric CO2 to be removed by natural processes, and some will remain for thousands of subsequent years.

How is the climate expected to change in the future?

Future warming of the climate is inevitable for many years due to the greenhouse gases already added to the atmosphere and the heat that has been taken up by the oceans.

Climate-model simulations further project that heavy precipitation events will continue to become more intense and frequent, leading to increased precipitation totals from the strongest storms. This projection has important implications for water-resource management and flood control. The simulations also indicate the likelihood of longer dry spells between precipitation events in the subtropics and lower-middle latitudes, with shorter dry spells projected for higher latitudes where mean precipitation is expected to increase. Continued warming also implies a reduction of winter snow accumulations in favor of rain in many places, and thus a reduced spring snowpack. Rivers now fed by snowmelt will experience earlier spring peaks and reduced warm-season flows. Widespread retreat of mountain glaciers is expected to eventually lead to reduced dry season flows for glacier-fed rivers. Drought is projected to increase over Africa, Europe, and much of the North American continental interior, and particularly the southwest United States. However, natural variations in world ocean conditions at decadal scale, such as those in the North Pacific and North Atlantic basins, could offset or enhance such changes in the next few decades. For the longer term, paleoclimatic observations suggest that droughts lasting decades are possible and that these prolonged droughts could occur with little warning.

Technological, economic, and policy choices in the near future will determine the extent of future impacts of climate change. Science-based decisions are seldom made in a context of absolute certainty. National and international policy discussions should include consideration of the best ways to both adapt to and mitigate climate change. Mitigation will reduce the amount of future climate change and the risk of impacts that are potentially large and dangerous. At the same time, some continued climate change is inevitable, and policy responses should include adaptation to climate change. Prudence dictates extreme care in accounting for our relationship with the only planet known to be capable of sustaining human life.

I recommend that everyone read the full statement.

[dabize]

I'm curious as to whether the mets here are AMS members and whether they support this statement.

The silence in response to this post seems profound, though.

[TerryM]

30 years late - but still welcome

Terry

[Vergent]

PhilipS,

Thanks for that, I was looking for a signature.

Verg

[WeatherRusty]

Where are the usual this is nothing but an appeal to authority posts? Or the hierarchy does not represent the body type posts?

The skeptics have failed to convince scientific institutions, but they have done a good job on the general public and in the political arena.

[dabize]

Where are the usual this is nothing but an appeal to authority posts? Or the hierarchy does not represent the body type posts?

The skeptics have failed to convince scientific institutions, but they have done a good job on the general public and in the political arena.

Maybe the existence of this sort of thing?......

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