Groundhogs, tornadoes, hurricanes, and the new IPCC report

By: Dr. Jeff Masters , 17:44:GMT den 02. februar 2007

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Punxsutawney Phil, the fearless groundhog forecaster of Punxsutawney, Pennsylvania, did not see his shadow this morning, signifying that winter will come to an early close. Phil can expect this to be a common occurrence in the coming millennia, according to the newly released Summary of Policy Makers issued today by the United Nations sponsored Intergovernmental Panel on Climate Change (IPCC). In their fourth report since 1990, the IPCC offers its strongest language yet that Earth's climate is warming and humans are largely responsible:

"Warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global mean sea level."

"Most of the observed increase in globally averaged temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations. Discernible human influences now extend to other aspects of climate, including ocean warming, continental-average temperatures, temperature extremes, and wind patterns."


Earth has warmed, sea levels have begun to rise at an accelerated rate, and Northern Hemisphere snow cover has decreased substantially over the past 150 years (Figure 1). These facts are not controversial. The big change from the IPCC's last report, in 2001, is the level of confidence on if humans are to blame. In that report, human-emitted (anthropogenic) greenhouse gases were estimated to be likely responsible for Earth's temperature increase (67-90% chance), while the new report says it is very likely (greater than 90% chance).


Figure 1. Observed changes in (a) global average surface temperature; (b) global average sea level rise from tide gauge (blue) and satellite (red) data and (c) Northern Hemisphere snow cover for March-April. All changes are relative to corresponding averages for the period 1961-1990. Smoothed curves represent decadal averaged values while circles show yearly values. The shaded areas are the uncertainty intervals estimated from a comprehensive analysis of known uncertainties (a and b) and from the time series (c). Image credit: FIGURE SPM-3 from the Summary of Policy Makers from the 2007 Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report.

Predicted temperature rise
The 2007 IPCC report predicts temperature rises of 1.1 - 6.4°C (2 - 11.5°F) by 2100. This is a wider range than the 1.4 - 5.8°C increase given in the 2001 report. However, the 2007 report goes on to say that their best estimate for temperature rise is 1.8 - 4°C (3.2 - 7.1°F).

Predicted sea level rise
The 2007 report predicts that sea level rise by 2100 will be .6 - 1.9 feet (18 - 58 cm). An additional 3.9 to 7.8 inches (10 to 20 cm) are possible if the recent surprising melting of polar ice sheets continues. The 2001 IPCC report gave a much wider range for sea level rise: .3 - 2.9 feet (8 - 88 cm).

What does the IPCC say about stronger hurricanes?
The IPCC did a good job with their treatment of how global warming is affecting hurricanes. Here's their carefully worded statement on the observed changes:

There is observational evidence for an increase of intense tropical cyclone activity in the North Atlantic since about 1970, correlated with increases of tropical sea surface temperatures. There are also suggestions of increased intense tropical cyclone activity in some other regions where concerns over data quality are greater. Multi-decadal variability and the quality of the tropical cyclone records prior to routine satellite observations in about 1970 complicate the detection of long-term trends in tropical cyclone activity. There is no clear trend in the annual numbers of tropical cyclones.


Later in the report, there is a table that shows that there has likely (>66% chance) been an increase in strong hurricanes since 1970 in some regions. It isn't mentioned, but the Atlantic is the region where this increase has been most notable. Also in that table is the assertion that it is more likely than not (>50% chance) that there has been a human contribution to this trend. This statement was leaked to the press yesterday, and resulted in speculation that the IPCC concluded that stronger hurricanes like Katrina were due to human-caused global warming. However, there is a footnote on the table, which wasn't part of yesterday's leaked press reports: "Magnitude of anthropogenic contributions not assessed. Attribution for these phenomena based on expert judgment rather than formal attribution studies."

In other words, the link between stronger hurricanes and global warming is a theory (expert judgment) and is not a conclusion of the IPCC. It is reasonable to theorize that some human contribution is responsible for the increase in strong hurricanes in the Atlantic since 1970, since this increase does correlate so well with the observed increase in sea surface temperatures. However, as mentioned in the earlier paragraph, it is difficult to make a strong statement saying that global warming is responsible for stronger hurricanes, due to the high natural variability of these storms and the poor observational record: "multi-decadal variability and the quality of the tropical cyclone records prior to routine satellite observations in about 1970 complicate the detection of long-term trends in tropical cyclone activity." The IPCC table is confusing, and I believe it was a mistake to assign a probability of how likely a human contribution to hurricane intensity has been. There is not enough good science to make a sound judgment, and this section of the table should have been left blank.

Finally, the IPCC projection for how climate change will affect hurricanes in the future is pretty non-controversial, since they don't attach any numbers saying how large these effects will be:

Based on a range of models, it is likely that future tropical cyclones (typhoons and hurricanes) will become more intense, with larger peak wind speeds and more heavy precipitation associated with ongoing increases of tropical SSTs. There is less confidence in projections of a global decrease in numbers of tropical cyclones. The apparent increase in the proportion of very intense storms since 1970 in some regions is much larger than simulated by current models for that period.


Overall, the IPCC statements on hurricanes are very similar to those adopted by the World Meteorological Organization (WMO) in December, as I discussed in an earlier blog. The WMO report concluded, "Though there is evidence both for and against the existence of a detectable anthropogenic signal in the tropical cyclone climate record to date, no firm conclusion can be made on this point."

What does the IPCC say about stronger tornadoes?
In the wake of today's devastating tornadoes that swept through Central Florida, killing at least 19 people, it is important to ask how climate change might be affecting tornadoes. Well, we don't have good enough long-term observational records of tornadoes to tell, and climate models don't shed any light on the issue, either. Here's the relevant statement in the 2007 IPCC report:

There is insufficient evidence to determine whether trends exist in small scale phenomena such as tornadoes, hail, lighting, and dust storms.

I'll have much more on the IPCC report next week, as will Dr. Ricky Rood of the University of Michigan, who will be writing in our new featured Climate Change blog. Who knows, if we want to collect a quick $10,000, we can "thoughtfully explore the limitations of climate model outputs", as explained in an article posted by the UK Guardian today.


Jeff Masters

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Display: 0, 50, 100, 200 Sort: Newest First - Order Posted

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194. Skyepony (Mod)
14:53:GMT den 05. februar 2007
29 Dead in Indonesia Flood; 340,000 Flee
Member Since: august 10, 2005 Posts: 175 Comments: 38201
193. tornadodude
14:43:GMT den 05. februar 2007
Just before sunrise the temperature at the Indianapolis International Airport fell to minus 5. This is the coldest temperature recorded at the airport since Christmas Eve 2004 when the mercury also fell to minus 5. NWS Indianapolis.....

Nice cold reception for the Colts... But, They won the hot one!

Member Since: juni 28, 2006 Posts: 25 Comments: 8360
192. tornadodude
14:35:GMT den 05. februar 2007

... Coldest air in over 2 years at Indianapolis...

Early this morning the temperature at the Indianapolis
International Airport fell to minus 4. This is the coldest
temperature recorded at the Airport since Christmas eve 2004 when
when a reading of minus 5 was recorded.


morning guys... go Colts!

Member Since: juni 28, 2006 Posts: 25 Comments: 8360
191. HadesGodWyvern (Mod)
04:20:GMT den 05. februar 2007
Eastern Australia - TCWC Brisbane

Tropical Cyclone Advise #1
==========================

Tropical Low
17.0S 146.2E - 20 knots 1003 hPa

moving southeast at 2 knots

The Tropical Low is centered about 46 km east of Cairns or 60 km north-northeast of Innisfail and should gradually intensify over the next 24 hours.

Tropical Cyclone [Cat 1 / 35-45 kts] expected in 36 to 48 hours.

next Tropical Advise at about 7:00am UTC (5:00pm EST)

--------------
Central Indian Ocean - TCWC Perth

Tropical Low [1006 hPa]
location: 5S 96E (900 km north of Cocos Islands)

Tropical Cyclone Potential
=======================
Tuesday = Low
Wednesday = Moderate
Thursday = High
Member Since: mai 24, 2006 Posts: 51 Comments: 45628
190. Skyepony (Mod)
03:56:GMT den 05. februar 2007
Can't they put just a little bit of blue on this forecast for the year...somewhere???? Just to make us feel like we might not fry?

Member Since: august 10, 2005 Posts: 175 Comments: 38201
189. Patrap
03:34:GMT den 05. februar 2007
Chicago Current Temp -1.2F..LOL!..Happy Homecoming Fans and Players! New Orleanian Peyton Wins MVP!..Sweeeeeeeeeeeeeeeeeeeeeeeeeeeeet!
Member Since: juli 3, 2005 Posts: 426 Comments: 128668
188. Skyepony (Mod)
03:15:GMT den 05. februar 2007
The Ice Hotel
Member Since: august 10, 2005 Posts: 175 Comments: 38201
185. ryang
01:20:GMT den 05. februar 2007
Hello.No one here,So i will update my blog.
Member Since: august 25, 2006 Posts: 329 Comments: 12440
184. catastropheadjuster
01:19:GMT den 05. februar 2007
Yeah Prince is singing Purple Rain
Member Since: august 24, 2006 Posts: 21 Comments: 3678
183. catastropheadjuster
01:17:GMT den 05. februar 2007
Yeap Prince is singing Purple Rain
Member Since: august 24, 2006 Posts: 21 Comments: 3678
182. Skyepony (Mod)
01:08:GMT den 05. februar 2007
That link that Jeff left us on collecting the $10000, a must read... In there is this link, really good about the slowing of the gulf stream. Slowed 30% in the last 12 years.

I hear Prince is on:)
Member Since: august 10, 2005 Posts: 175 Comments: 38201
181. Skyepony (Mod)
00:55:GMT den 05. februar 2007
TayTay it was annular for a solid day & 1/2. It has weaked now...shear got her.



I's gonna look at the rain rates there at the super bowl on Nexrad, both they & NRL are down..
By the radar it's the rainest spot around:)
Member Since: august 10, 2005 Posts: 175 Comments: 38201
180. tornadodude
23:17:GMT den 04. februar 2007
go Colts!
Member Since: juni 28, 2006 Posts: 25 Comments: 8360
179. ryang
23:15:GMT den 04. februar 2007
Hey Kris.
Member Since: august 25, 2006 Posts: 329 Comments: 12440
178. weatherboykris
23:14:GMT den 04. februar 2007
Was Dora annular at any point?


They claim it was,but given it's rapid weakening over the past 24h with no land interaction,I find that hard to believe.It just appeared Annular.
Member Since: desember 9, 2006 Posts: 125 Comments: 11346
177. Patrap
21:40:GMT den 04. februar 2007
CIMSS MIMIC DORA..Link
Member Since: juli 3, 2005 Posts: 426 Comments: 128668
176. TayTay
21:26:GMT den 04. februar 2007
Was Dora annular at any point?
175. catastropheadjuster
21:02:GMT den 04. februar 2007
Well I will be back cause i have to go to the laundremat to do clothes washer tore up last night. Gosh I'm gonna have sooo much fun. LOL
Member Since: august 24, 2006 Posts: 21 Comments: 3678
174. ryang
21:01:GMT den 04. februar 2007
Hi TS2.
Member Since: august 25, 2006 Posts: 329 Comments: 12440
173. Thunderstorm2
20:58:GMT den 04. februar 2007
Hi everyone
Member Since: desember 22, 2006 Posts: 129 Comments: 7608
172. catastropheadjuster
20:58:GMT den 04. februar 2007
Yes We already have a plan and food stocked up. potted meat and vienne sausages last along time. and of course I've got other stuff to but I have a big storage bin that i keep things in and i stock up all winter long so I'm not doing it at the last minute like alot of folks do around here. I have never understood why they wait til the last minute and then there's alot of fights over things it gets really crazy to crazy for me.
Member Since: august 24, 2006 Posts: 21 Comments: 3678
171. ryang
20:55:GMT den 04. februar 2007
Thanks 23.Nice post.
Member Since: august 25, 2006 Posts: 329 Comments: 12440
170. hurricane23
20:39:GMT den 04. februar 2007
catastropheadjuster whats up?

If La Nina conditions are present the overall atmosphere will indeed be more conducive for tropical developement but this could also mean a busy season number wise with earlier recurvature meaning north carolina and florida are probably to of my 2 picks at seeing some activity this season.It will all depend on how steering currents eventually set up.It really doesn't matter if we have 50 storms develope out in the middle of now were because the ones that actually make landfall are the ones that actually have the greatest impact.I never focus attention on numbers predicted cause it only takes one to ruin lives.Overall lets see how things evolve in the coming months and hopefully the U.S. is once again spared.

My best advice is just be ready come june1 with an emergency plan in place for you and your family.Adrian
Member Since: mai 14, 2006 Posts: 8 Comments: 13804
169. ryang
20:38:GMT den 04. februar 2007
Yes.
Member Since: august 25, 2006 Posts: 329 Comments: 12440
168. catastropheadjuster
20:35:GMT den 04. februar 2007
who me?
Member Since: august 24, 2006 Posts: 21 Comments: 3678
167. ryang
20:32:GMT den 04. februar 2007
Come to my blog.
Member Since: august 25, 2006 Posts: 329 Comments: 12440
166. catastropheadjuster
20:31:GMT den 04. februar 2007
Is anyone here or is everyone getting ready for the Super bowl?
Member Since: august 24, 2006 Posts: 21 Comments: 3678
165. catastropheadjuster
20:27:GMT den 04. februar 2007
Hey H23 So I see La Nina is going to more than likely come into effect for Hurricane Season. Looks like it might be a interesting season this year. What do you think.
Member Since: august 24, 2006 Posts: 21 Comments: 3678
164. hurricane23
20:13:GMT den 04. februar 2007
If the POAMA model is correct the atlantic basin will see La Nina conditions at some point during this upcoming hurricane season.




Member Since: mai 14, 2006 Posts: 8 Comments: 13804
163. hurricane23
20:05:GMT den 04. februar 2007
Good afternoon,

A gloomy day across south florida today with on and off showers all day.Also a tad bit on the cool side.
Member Since: mai 14, 2006 Posts: 8 Comments: 13804
162. ryang
18:24:GMT den 04. februar 2007
Thanks Pottery.
Member Since: august 25, 2006 Posts: 329 Comments: 12440
161. pottery
18:23:GMT den 04. februar 2007
For those that are NOT watching the Super bowl...go to www.radiotrinbago.com..................... a musical treat is in progress. I'm there in 30 mins !!!!!!!!!!!
Member Since: Oktober 24, 2005 Posts: 0 Comments: 24390
159. Thunderstorm2
16:46:GMT den 04. februar 2007
Hi JFLORIDA & STL
Member Since: desember 22, 2006 Posts: 129 Comments: 7608
156. Thunderstorm2
16:21:GMT den 04. februar 2007
Is anyone on
Member Since: desember 22, 2006 Posts: 129 Comments: 7608
153. HurricaneMyles
15:59:GMT den 04. februar 2007
Kris...down here in S Fl we have had a warmer then ussual winter, but I'm not complaining. I'm happy we havent had one freeze when normally we've had 2-3. The 3-4 'cold' fronts were more refreshing then cold. However, for a while the western US was very cold. Now its moved over to the midwest and NE states.
Member Since: januar 12, 2006 Posts: 5 Comments: 827
151. weatherboykris
15:55:GMT den 04. februar 2007
JFL,I'm not talking about what is shown on the model runs,I'm talking about what actually happened.Florida has had what,3 major cold fronts this year?Wimpy winter
Member Since: desember 9, 2006 Posts: 125 Comments: 11346
150. weatherboykris
15:53:GMT den 04. februar 2007
Ahh, what have been the huge surges of cold air during the past few weeks then?


Those haven't really penetrated into the SE.That's the region of the country I'm talking about.This winter has been so boring.Only 116 Days
Member Since: desember 9, 2006 Posts: 125 Comments: 11346
148. weathersp
15:50:GMT den 04. februar 2007
FOR MORE INFORMATION ON THE NEW EF-SCALE...PLEASE SEE THE FOLLOWING BLOG:Link

The latest GFS run just shows clipper after clipper of massively cold air penetrateing the Ohio valley area bringing deathly cold temperatures. The moisture steam continues but moves further down south bringing day after day of rain on the keys and south Florida.
Member Since: januar 14, 2007 Posts: 17 Comments: 4140
147. HurricaneMyles
15:50:GMT den 04. februar 2007
Ahh, what have been the huge surges of cold air during the past few weeks then?
Member Since: januar 12, 2006 Posts: 5 Comments: 827
146. weatherboykris
15:47:GMT den 04. februar 2007
JFL,we never had a wintertime pattern emerge!
Member Since: desember 9, 2006 Posts: 125 Comments: 11346

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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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