Climate Change Questions

[WeatherFanMatt]

Hello, I'm a weather enthusiast, and I have a few questions regarding how fast we are seeing these climatic changes, and would like answers from people that know about meteorolgy, not some idiot on Yahoo Answers.

 

So, part of Climate Change, we are supposed to experience stronger storms due to Climate Change. What part of Climate change causes more storms? Warmer seas?

 

1. So, as I see the idea of "Stronger and more storms" quite frequently in the news, they never say "when", just the "future". Now, this is not good enough for me. I was wondering if any of you have a better idea of when it will become noticeable that stronger storms are becoming more frequent, as I don't see signs that storms are becoming stronger yet.

 

2. It is possible that in our lifetimes, we will be 100% void of snow? (In the United States). 

 

3. Why is the tornado count decreasing every year? Is it possible in our life times, tornadoes will be quite rare?

 

4. Why is winter weather stretching far into spring? How many times have we seen this happen in the past? Is it normal?

 

5. Is it possible, that we could see a huge jump in hurricanes in the next 1-3 years? Going way above the hurricane count average? Or will it take a longer slower process for hurricanes to become more extreme and frequent.

 

6. When will the ocean levels rise to a level were it becomes noticeable from a quick look at the beach. What I mean by this, is when will the sea levels rise to a level that coastal cities and communities will be flooded.

 

The whole point of these questions is to get a point on how fast, and when we are expected to see devestating changes in result of climate change, and whether it will happen during our lifetimes.

 

Appreciate any answers, and thank you for your time.

[WestWind]

At mid latitudes in the US, linear regression shows a temperature rise of about 1.5 degrees Fahrenheit over the past 30 years.  This corresponds to roughly the equivalent of moving a mile south each year.  So the change is not rapid, but over time it adds up.  Rates of temperature change are higher closer to the poles, and lower near the equator. 

 

I'll take a shot at your questions.

 

1. Yes, storms do become stronger, because they have more heat to work with.  The amount of energy in saturated air roughly doubles for every 20 degree Fahrenheit increase in temperature.  So if the temperature rises 2 degrees Fahrenheit over the next 40 years (the current rate of rise), in storms will be 10% more powerful on average.  In addition, hurricanes tend not to form at all until some minimum temperature.  In the Atlantic, there is a strong peak in hurricane activity around Labor Day.  As temperatures continue warming, expect the peak to be less sharp with more hurricanes earlier in August and later into late September.

 

2. Highly unlikely.  Assuming someone expects to live 50 more years from now, they can expect to see a temperature rise of about 2.5 degrees, which is equivalent to moving about 50 miles south.

 

3. The number of tornadoes is highly variable between years.  It is not decreasing.  The number of deaths from tornadoes and severe weather in general is decreasing though, mainly due to improved prediction and warnings.

 

4. It could possibly be coincidence, although there may be some effect from less arctic ice cover during the summer.  Arctic ice extent has decreased noticeably in recent years as a result of warming.  In the fall, this means less temperature contrast to drive the jet stream, resulting in an often stagnant and warm pattern later into the fall.  With more open water lasting into the winter, and warmer temperatures, land areas in the arctic have more moisture to work with for snow.  Although winter temperatures are warmer, more snow falls due to the increased moisture.  Thus the snow may melt later in the spring than previously due to the larger amount, leading to cooler temperatures for the first part of spring.

 

5. See #1.  Hurricanes are likely to show the most dramatic increase of all storm types, due to their season being extended.  But this trend has already started - it's not like there is going to be a sudden change.  Like tornadoes, there is a large variability in the number of hurricanes from year to year which can mask the trend in the short term.

 

6. Ocean levels are presently rising on the order of a millimeter per year.  This rate could accelerate as the polar ice caps melt, but I doubt the change would be more than an order of magnitude.  Assuming a rate of rise 5 times the present rate, this would only be 25 centimeters (10 inches) in 50 years.  So only areas right on the shore would be affected in the next 50 years (at least in the US).

 

Hope that helps.  I'm not a meteorologist, so others with more knowledge feel free to correct anything I have stated incorrectly above.

 

[skierinvermont]

At mid latitudes in the US, linear regression shows a temperature rise of about 1.5 degrees Fahrenheit over the past 30 years.  This corresponds to roughly the equivalent of moving a mile south each year.  So the change is not rapid, but over time it adds up.  Rates of temperature change are higher closer to the poles, and lower near the equator. 

 

I'll take a shot at your questions.

 

1. Yes, storms do become stronger, because they have more heat to work with.  The amount of energy in saturated air roughly doubles for every 20 degree Fahrenheit increase in temperature.  So if the temperature rises 2 degrees Fahrenheit over the next 40 years (the current rate of rise), in storms will be 10% more powerful on average.  In addition, hurricanes tend not to form at all until some minimum temperature.  In the Atlantic, there is a strong peak in hurricane activity around Labor Day.  As temperatures continue warming, expect the peak to be less sharp with more hurricanes earlier in August and later into late September.

 

2. Highly unlikely.  Assuming someone expects to live 50 more years from now, they can expect to see a temperature rise of about 2.5 degrees, which is equivalent to moving about 50 miles south.

 

3. The number of tornadoes is highly variable between years.  It is not decreasing.  The number of deaths from tornadoes and severe weather in general is decreasing though, mainly due to improved prediction and warnings.

 

4. It could possibly be coincidence, although there may be some effect from less arctic ice cover during the summer.  Arctic ice extent has decreased noticeably in recent years as a result of warming.  In the fall, this means less temperature contrast to drive the jet stream, resulting in an often stagnant and warm pattern later into the fall.  With more open water lasting into the winter, and warmer temperatures, land areas in the arctic have more moisture to work with for snow.  Although winter temperatures are warmer, more snow falls due to the increased moisture.  Thus the snow may melt later in the spring than previously due to the larger amount, leading to cooler temperatures for the first part of spring.

 

5. See #1.  Hurricanes are likely to show the most dramatic increase of all storm types, due to their season being extended.  But this trend has already started - it's not like there is going to be a sudden change.  Like tornadoes, there is a large variability in the number of hurricanes from year to year which can mask the trend in the short term.

 

6. Ocean levels are presently rising on the order of a millimeter per year.  This rate could accelerate as the polar ice caps melt, but I doubt the change would be more than an order of magnitude.  Assuming a rate of rise 5 times the present rate, this would only be 25 centimeters (10 inches) in 50 years.  So only areas right on the shore would be affected in the next 50 years (at least in the US).

 

Hope that helps.  I'm not a meteorologist, so others with more knowledge feel free to correct anything I have stated incorrectly above.

 

I'll take a shot. I agree with most of Westwind has said, but disagree on some, and have some more to add.

 

 

1. Not all storms become stronger. There is just potential for stronger storms because there is more energy to work with. You'll note for example that the heaviest rainfall records in 24-hr periods come from the tropics. The best and only slightly over-simplified way of thinking of things is that climate zones will gradually shift north. Storms need temperature contrasts too, which are partially assisted by blocking and other circulation patterns. It's not totally clear how blocking and other circulation patterns will change. There has been some hypothesizing that blocking will increase, but it's not totally proven yet. 

 

There is some evidence of increasing extreme precipitation events globally (both dry and wet).

 

2. Not likely. Somebody born today and lives 100 years, and if climate sensitivity is on the very high end of what we think it might be, could witness winter U.S. warming of close to 20F, which would be enough to make snowfall rare and limited to northern high altitudes like parts of Montana. But that is a worst case scenario. 

 

3. This is incorrect. The tornado count has been increasing, not decreasing. But this is due to improved detection and reporting. F3+ tornadoes show little long-term trend. It is unclear whether U.S. tornadoes would increase or decrease with AGW. Canadian tornadoes probably will increase. 

 

4. Globally this is not true. Globally snow cover extent in spring has been decreasing. The trend over the last 50 years has been 2 or 3 million sq km less snow cover in March and April. All locations globally show long-term spring time warming. I'm not sure if you are referring to a local regional trend?

 

5. Westwind is wrong about this. Hurricanes are projected to decrease in frequency with AGW by 0-10% while strong hurricanes are expected to increase in frequency 0-10%. And this is at the end of a 3C warming by 2100 scenario. There is uncertainty but no evidence to expect large changes.

 

6. Again, Westwind is wrong about the present rate. The present rate (30-yr average) has been just over 3mm/yr, not 1mm/yr. There is likely going to be some acceleration in this rate. I would guess, based on research I have read, that sea level rise in the next 50 years will be 5-20" most likely around 12". The 10" of sea level rise over the previous century has already caused some small increases in coastal flooding in the most sensitive areas. An additional 12" will cause a significant increase in coastal flooding, but probably not obvious to the individual without the aggregated data. I'd guess sea level rise by the end of the century will be 15-60" most likely around 30". That should be very obvious to anybody who lives on the coast, and the high end of that range would be very damaging and costly. Sea level rise after 2100 will likely continue to accelerate. 

[Jonger]

At mid latitudes in the US, linear regression shows a temperature rise of about 1.5 degrees Fahrenheit over the past 30 years.  This corresponds to roughly the equivalent of moving a mile south each year.  So the change is not rapid, but over time it adds up.  Rates of temperature change are higher closer to the poles, and lower near the equator. 

 

I'll take a shot at your questions.

 

1. Yes, storms do become stronger, because they have more heat to work with.  The amount of energy in saturated air roughly doubles for every 20 degree Fahrenheit increase in temperature.  So if the temperature rises 2 degrees Fahrenheit over the next 40 years (the current rate of rise), in storms will be 10% more powerful on average.  In addition, hurricanes tend not to form at all until some minimum temperature.  In the Atlantic, there is a strong peak in hurricane activity around Labor Day.  As temperatures continue warming, expect the peak to be less sharp with more hurricanes earlier in August and later into late September.

 

2. Highly unlikely.  Assuming someone expects to live 50 more years from now, they can expect to see a temperature rise of about 2.5 degrees, which is equivalent to moving about 50 miles south.

 

3. The number of tornadoes is highly variable between years.  It is not decreasing.  The number of deaths from tornadoes and severe weather in general is decreasing though, mainly due to improved prediction and warnings.

 

4. It could possibly be coincidence, although there may be some effect from less arctic ice cover during the summer.  Arctic ice extent has decreased noticeably in recent years as a result of warming.  In the fall, this means less temperature contrast to drive the jet stream, resulting in an often stagnant and warm pattern later into the fall.  With more open water lasting into the winter, and warmer temperatures, land areas in the arctic have more moisture to work with for snow.  Although winter temperatures are warmer, more snow falls due to the increased moisture.  Thus the snow may melt later in the spring than previously due to the larger amount, leading to cooler temperatures for the first part of spring.

 

5. See #1.  Hurricanes are likely to show the most dramatic increase of all storm types, due to their season being extended.  But this trend has already started - it's not like there is going to be a sudden change.  Like tornadoes, there is a large variability in the number of hurricanes from year to year which can mask the trend in the short term.

 

6. Ocean levels are presently rising on the order of a millimeter per year.  This rate could accelerate as the polar ice caps melt, but I doubt the change would be more than an order of magnitude.  Assuming a rate of rise 5 times the present rate, this would only be 25 centimeters (10 inches) in 50 years.  So only areas right on the shore would be affected in the next 50 years (at least in the US).

 

Hope that helps.  I'm not a meteorologist, so others with more knowledge feel free to correct anything I have stated incorrectly above.

 

I'll take a shot. I agree with most of Westwind has said, but disagree on some, and have some more to add.

 

 

1. Not all storms become stronger. There is just potential for stronger storms because there is more energy to work with. You'll note for example that the heaviest rainfall records in 24-hr periods come from the tropics. The best and only slightly over-simplified way of thinking of things is that climate zones will gradually shift north. Storms need temperature contrasts too, which are partially assisted by blocking and other circulation patterns. It's not totally clear how blocking and other circulation patterns will change. There has been some hypothesizing that blocking will increase, but it's not totally proven yet. 

 

There is some evidence of increasing extreme precipitation events globally (both dry and wet).

 

2. Not likely. Somebody born today and lives 100 years, and if climate sensitivity is on the very high end of what we think it might be, could witness winter U.S. warming of close to 20F, which would be enough to make snowfall rare and limited to northern high altitudes like parts of Montana. But that is a worst case scenario. 

 

3. This is incorrect. The tornado count has been increasing, not decreasing. But this is due to improved detection and reporting. F3+ tornadoes show little long-term trend. It is unclear whether U.S. tornadoes would increase or decrease with AGW. Canadian tornadoes probably will increase. 

 

4. Globally this is not true. Globally snow cover extent in spring has been decreasing. The trend over the last 50 years has been 2 or 3 million sq km less snow cover in March and April. All locations globally show long-term spring time warming. I'm not sure if you are referring to a local regional trend?

 

5. Westwind is wrong about this. Hurricanes are projected to decrease in frequency with AGW by 0-10% while strong hurricanes are expected to increase in frequency 0-10%. And this is at the end of a 3C warming by 2100 scenario. There is uncertainty but no evidence to expect large changes.

 

6. Again, Westwind is wrong about the present rate. The present rate (30-yr average) has been just over 3mm/yr, not 1mm/yr. There is likely going to be some acceleration in this rate. I would guess, based on research I have read, that sea level rise in the next 50 years will be 5-20" most likely around 12". The 10" of sea level rise over the previous century has already caused some small increases in coastal flooding in the most sensitive areas. An additional 12" will cause a significant increase in coastal flooding, but probably not obvious to the individual without the aggregated data. I'd guess sea level rise by the end of the century will be 15-60" most likely around 30". That should be very obvious to anybody who lives on the coast, and the high end of that range would be very damaging and costly. Sea level rise after 2100 will likely continue to accelerate. 

On #2. Who said a 20F rise in temp is even considered possible? Anything more than 5F seems to be hard to imagine, 20F seems like alarmist nonsense.

[skierinvermont]

On #2. Who said a 20F rise in temp is even considered possible? Anything more than 5F seems to be hard to imagine, 20F seems like alarmist nonsense.

 

 

The high emissions scenario (RCP 8.5) has a confidence interval of warming by 2081-2100 vs 1986-2005 of 2.5-5C globally. 

 

However, over land warming is greater. The confidence interval is 3.4-6.6C. 

 

Over mid-latitude winter, warming may be even slightly greater than that. Probably a high end of the confidence interval close to 8C.

 

Then account for the fact that a kid born today that lives to 100 dies in 2113, a good 20 years after the 2081-2100 end date, and you get an additional 1-2C of warming in mid-latitude land winter. That gets us close to 10C, or 20F.

 

This represents a worst case scenario because it assumes high emissions and high climate sensitivity. High emissions are certainly not out of the question, especially if we do nothing significant to reduce them (like a carbon tax, cap and trade etc.). A climate sensitivity of 5C+ is a low probability assumption (<10%). 

 

The other reason the number sounds big is it is for land-based mid-latitude winter. Warming is fastest in winter, over land, and the higher in latitude you go. For example, arctic winter warming in RCP 8.5 is as high as 15-30F by 2081-2100 (possibly as high as 40F by 2113). 

 

Most likely, assuming a more moderate emissions scenario and climate sensitivity, U.S. winters would warm about 6F. The "most likely" scenario is still greater than your "max" idea, probably because you are thinking of global annual #s instead of land, mid-latitude, winter #s. The biggest difference is land vs globe (which is 70% water). 

[ORH_wxman]

The high emissions scenario (RCP 8.5) has a confidence interval of warming by 2081-2100 vs 1986-2005 of 2.5-5C globally. 

 

However, over land warming is greater. The confidence interval is 3.4-6.6C. 

 

Over mid-latitude winter, warming may be even slightly greater than that. Probably a high end of the confidence interval close to 8C.

 

Then account for the fact that a kid born today that lives to 100 dies in 2113, a good 20 years after the 2081-2100 end date, and you get an additional 1-2C of warming in mid-latitude land winter. That gets us close to 10C, or 20F.

 

This represents a worst case scenario because it assumes high emissions and high climate sensitivity. High emissions are certainly not out of the question, especially if we do nothing significant to reduce them (like a carbon tax, cap and trade etc.). A climate sensitivity of 5C+ is a low probability assumption (<10%). 

 

The other reason the number sounds big is it is for land-based mid-latitude winter. Warming is fastest in winter, over land, and the higher in latitude you go. For example, arctic winter warming in RCP 8.5 is as high as 15-30F by 2081-2100 (possibly as high as 40F by 2113). 

 

Most likely, assuming a more moderate emissions scenario and climate sensitivity, U.S. winters would warm about 6F. The "most likely" scenario is still greater than your "max" idea, probably because you are thinking of global annual #s instead of land, mid-latitude, winter #s. The biggest difference is land vs globe (which is 70% water). 

 

 

Contiguous US Winters have been warming at a rate of 0.17F per decade since records began in the late 1800s. 6F still seems awfully high. Obviously the climate models are spitting out what they are spitting out, but we'll need to see some drastic acceleration soon akin to the 1990s warming. The only period of 3+ decades with comparable rates to get 6F over a century is if we start the trend in the late 1970s which was the coldest 3 year period of winters on record in the US. Or if we start it around 1910 (which had 4 of the top 10 coldest winters within 8 years) and end it near 1940. 

[Jonger]

The high emissions scenario (RCP 8.5) has a confidence interval of warming by 2081-2100 vs 1986-2005 of 2.5-5C globally. 

 

However, over land warming is greater. The confidence interval is 3.4-6.6C. 

 

Over mid-latitude winter, warming may be even slightly greater than that. Probably a high end of the confidence interval close to 8C.

 

Then account for the fact that a kid born today that lives to 100 dies in 2113, a good 20 years after the 2081-2100 end date, and you get an additional 1-2C of warming in mid-latitude land winter. That gets us close to 10C, or 20F.

 

This represents a worst case scenario because it assumes high emissions and high climate sensitivity. High emissions are certainly not out of the question, especially if we do nothing significant to reduce them (like a carbon tax, cap and trade etc.). A climate sensitivity of 5C+ is a low probability assumption (<10%). 

 

The other reason the number sounds big is it is for land-based mid-latitude winter. Warming is fastest in winter, over land, and the higher in latitude you go. For example, arctic winter warming in RCP 8.5 is as high as 15-30F by 2081-2100 (possibly as high as 40F by 2113). 

 

Most likely, assuming a more moderate emissions scenario and climate sensitivity, U.S. winters would warm about 6F. The "most likely" scenario is still greater than your "max" idea, probably because you are thinking of global annual #s instead of land, mid-latitude, winter #s. The biggest difference is land vs globe (which is 70% water). 

 

Well, color me skeptical... Sorry. I'm just doubting CO2 is making that much of an impact now... Let alone that extreme.

[Jonger]

Contiguous US Winters have been warming at a rate of 0.17F per decade since records began in the late 1800s. 6F still seems awfully high. Obviously the climate models are spitting out what they are spitting out, but we'll need to see some drastic acceleration soon akin to the 1990s warming. The only period of 3+ decades with comparable rates to get 6F over a century is if we start the trend in the late 1970s which was the coldest 3 year period of winters on record in the US. Or if we start it around 1910 (which had 4 of the top 10 coldest winters within 8 years) and end it near 1940. 

 

The last decade, DJF averaged around 0.6 to 1.0 degree warmer than average over the lower 48. The highest was over the north central, the lowest was actually below the 100 year average in the gulf states. 20F would have to require a secondary heat source, like a newly formed Tatooine binary star. I'm 33 years old, I should be around to verify much of this warming within my lifetime.

[skierinvermont]

Contiguous US Winters have been warming at a rate of 0.17F per decade since records began in the late 1800s. 6F still seems awfully high. Obviously the climate models are spitting out what they are spitting out, but we'll need to see some drastic acceleration soon akin to the 1990s warming. The only period of 3+ decades with comparable rates to get 6F over a century is if we start the trend in the late 1970s which was the coldest 3 year period of winters on record in the US. Or if we start it around 1910 (which had 4 of the top 10 coldest winters within 8 years) and end it near 1940. 

 

.8C of warming globally has caused 2F of U.S. winter temp increase. The mean projection for the A1B scenario was 3C globally.. almost 4X more warming which would actually suggest nearly 8F more winter u.s. warming if the ratio stayed the same.

 

Warming in the 21st century is projected to be much faster because 1) CO2 is rising much faster 2) aerosols will be rising much slower or not at all

[skierinvermont]

Well, color me skeptical... Sorry. I'm just doubting CO2 is making that much of an impact now... Let alone that extreme.

 

 

CO2 has only increased 33% thus far and it is uncertain how much of that was cancelled by aerosols (which leads to uncertainty of what climate sensitivity is). 

 

Such a high amount of warming is possible (though unlikely) because

 

1) CO2 could increase a lot more than 33% over the next century, possibly 100%+ 

 

2) aerosols may increase much less or not at all

 

IF a very large portion of 20th century GHG warming was cancelled by aerosols, and IF GHGs increase 3X+ more in the 21st century than the 20th century, THEN extreme warming is possible.

 

Both IFs are possible, but unlikely. 

[skierinvermont]

The last decade, DJF averaged around 0.6 to 1.0 degree warmer than average over the lower 48. The highest was over the north central, the lowest was actually below the 100 year average in the gulf states. 20F would have to require a secondary heat source, like a newly formed Tatooine binary star. I'm 33 years old, I should be around to verify much of this warming within my lifetime.

 

 

See my last two responses. Also remember that .6-1F above average means 1.2-2F of warming has occurred. U.S. winter warming has been close to 2F. 

 

Also, 20F represents the most extreme worst case scenario. 5 or 6F of warming would be based on more probable assumptions about emissions and climate sensitivity. About 3X what has occurred thus far. 

 

Which makes sense, given globally warming is also expected to be about 3X what has occurred thus far. 

[ORH_wxman]

.8C of warming globally has caused 2F of U.S. winter temp increase. The mean projection for the A1B scenario was 3C globally.. almost 4X more warming which would actually suggest nearly 8F more winter u.s. warming if the ratio stayed the same.

 

Warming in the 21st century is projected to be much faster because 1) CO2 is rising much faster 2) aerosols will be rising much slower or not at all

 

 

2F in like 117 years. In 100 years its been less, about 1.7F...the 0.17F per decade I mentioned. I'm generally getting your argument, but if we're talking to the end of the 21st century, then I'd definitely take the under. I'd take the under even if it were 100 years from now in 2113.

 

But I guess that is because I take the 3C scenario on a global scale skeptically as well...preferring to side with the lower sensitivity estimates.

[skierinvermont]

2F in like 117 years. In 100 years its been less, about 1.7F...the 0.17F per decade I mentioned. I'm generally getting your argument, but if we're talking to the end of the 21st century, then I'd definitely take the under. I'd take the under even if it were 100 years from now in 2113.

 

But I guess that is because I take the 3C scenario on a global scale skeptically as well...preferring to side with the lower sensitivity estimates.

 

Right ... 3.3C in U.S. winter makes sense given a projected 3C globally. The real question is do we see 3C globally by 2100.

[WeatherFanMatt]

Thanks for answers guys!!

 

I have a few more questions:

 

1. When do most hurricanes hit the U.S Mainland? What months?

 

2. Is their a higher possibility that we could have a devestating hurricane this year compared to last year, or the previous years?

[SVT450R]

Thanks for answers guys!!

 

I have a few more questions:

 

1. When do most hurricanes hit the U.S Mainland? What months?

 

2. Is their a higher possibility that we could have a devestating hurricane this year compared to last year, or the previous years?

Go here lots of posters and useful information you could get your answers if you post it in there.

http://www.americanwx.com/bb/index.php/topic/38601-atlantic-tropical-action-2013/page-6