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Ned Potter is the science correspondent for ABC's "World News with Charles Gibson." He has reported on such topics as space exploration, the human genome and climate change.

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Rain and Climate

July 23, 2007 4:07 PM

It's been raining, unusually hard, in several parts of the world--England, China, India, and parts of the U.S.--and, quite by coincidence, there is a paper coming in this Thursday's edition of the journal Nature, reporting that, "for the first time, climate scientists have clearly detected the human fingerprint on changing global precipitation patterns over the last century." 

That phrase comes from the lead authors at Environment Canada, who worked with other scientists in Britain, Japan and the U.S.  They compared rainfall patterns since 1925 with the changes that fourteen different computer models of the climate said ought to have happened, and found that in large parts of the world, they match pretty well.

"We show," they write in the Nature paper, "that anthropogenic forcing [i.e., changes caused by human activity] has had a detectable influence on observed changes in average precipitation within latitudinal bands, and that these changes cannot be explained by internal climate variability or natural forcing."

They found much of the Northern Hemisphere and the southern tropics getting wetter over time, and some tropical regions just north of the Equator--notably the Sahel region in Africa--getting drier.

The abstract of the paper is HERE.  The full paper is not online without a subscription, but Nature does have a news piece of its own HERE

"This is a very important paper," says climate researcher Myles Allen of Oxford, in the Nature news piece. "It identifies the fingerprint of human influence."

There are some important caveats to remember:

--The rainfall records used in the paper are only on land (records at sea, before weather satellites, are spotty), so about two thirds of the planet cannot be measured. 

--Weather is not climate, so it's dangerous to say the bad rains today are necessarily connected with global changes.

--Could there be other factors at play?  Yes, of course, but this paper found the best match between actual rainfall and the computer models came when the models accounted for "anthropogenic" factors--the increase in greenhouse gases such as carbon dioxide.

There's been a lot of discussion over whether variations in the Sun's intensity could explain the warming of the last 20 years.  To that end, there's now a paper in Proceedings of the Royal Society, by a pair of British and Swiss scientists, saying that if anything, "all the trends in the Sun that could have had an influence on the Earth's climate have been in the opposite direction to that required to explain the observed rise in glboal mean temperatures."  The full paper is HERE.

Climate is always politically contentious.  Thoughts welcomed.

July 23, 2007 | Permalink | Share | User Comments (46)

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Anyone ever hear about Global Dimming? It is another man-made companion global problem that oddly enough counter-balances Global warming but is equally as harmful to mankind... look it up.

Posted by: Pudentaine | Jul 23, 2007 4:22:25 PM

I am not sure why the author of this piece would use the term contentious. There is no doubt amongst people with training in atmospheric dynamics/chemistry that anthropogenic forcing is the primary cause of global warming. Sounds like ABC might be afraid of offending the administration more than they feel obligated to present the simple and obvious facts.

Posted by: alden | Jul 23, 2007 4:25:49 PM

Where there is no rain (forest fires in several states) that is a sure sign of global warming. Where the same rain that did not fall in those states, is falling and causing floods, that, of course, is also a sure sign of global warming.
Anyone with any serious scientific training in stupidology will clearly see that we have a serious global rise in ChickenLittleitis on a global scale. Run for your life! Cluck, cluck!

Posted by: cluckcluck | Jul 23, 2007 4:36:20 PM

Not only should we cut our energy consumption to lessen global climate change, we should do it so we don't have to stick our nose in the Middle East hornet's nest every day of the year. The OPEC countries need our expertise and productivity more than we need their oil!

Posted by: rob | Jul 23, 2007 4:45:25 PM

Computer models huh? Just because you solve a few differential equations on a computer it is supposed to imply that you are getting the TRUTH? Unless you can start predicting the future (as opposed to "predicting" the past) SUCCESSFULLY AND REPEATEDLY it is not science, it is simply religion/politics. I think the wall-street modelers have finally moved over to modeling weather. You get paid no matter whether you are right or wrong because average person thinks sophisticated (i.e., 17th century math) and computers can't be wrong.
Incidentally, liberals think global warming is man-made and conservatives think it is not man-made. So that is how far this "science" has come. Of course there is no conservative and liberal branches of quantum mechanics or newtons laws. Is there? Because they are SCIENCE not religion or politics.
Just getting irritated by these extreme hippies. And a note against conservatives: Just because we are not causing global warming does not mean we should force ourselves to be energy inefficient or cause other sorts of pollution. Can we get a little balanced thought from the media please?

Posted by: hysteriawatch | Jul 23, 2007 4:56:12 PM

In science, statistical models are used to FORECAST the likelihood of an event happening, not PREDICT it like some astrologer/Defense Department undersecretary. And frankly, I don't see the word "predict" in this piece.

BTW, Wall Street makes very good bets based on weather (after all, they have the money and they're not hobbled by political appointees of the Bush administration) and the are driving the prices of resources steadily upward. If Hysteriawatch won't listen to science, perhaps he'll listen to his frat-boy betters at the investment banks.

Posted by: rob | Jul 23, 2007 5:01:32 PM

Isn't it interesting that the authors
note: --Weather is not climate, so it's dangerous to say the bad rains today are necessarily connected with global changes.

What are "bad rains" versus "good rains?


Posted by: Chuck | Jul 23, 2007 5:02:18 PM

Two years ago it was all the hurricanes that proved global warming was here. So, no hurricanes to speak of during the past two years.......

Is gobal warming over?

I don't think it is that simple (rain which has always been cyclical) to prove and scientists are just trying to make a buck.

Posted by: donbl | Jul 23, 2007 5:03:12 PM

I'm not a scientist but I am a thinker; Like humans, the dinosaurs grew into huge numbers during their time and I wonder if they effected their environment too? The great herds of herbivores would have created large amounts of greenhouse gasses. Maybe climate change is an unavoidable part of evolution itself? Creatures with walnuts for brains managed to survive over 300 million years, I can only hope humans can adjust and survive too.

Posted by: tony | Jul 23, 2007 5:04:02 PM

Hey Chuck, I think the "bad rains" are the flooding rains and the "good rains" are the rains that make flowers grow. All in all, it has been a strange summer. My area, the Hampton Roads region of Virginia, has been somewhat dry, not as much rain as in previous years, and has been significantly hotter as well. Also, what happened to this "active" hurricane season? Shouldn't we have had 2 or 3 storms by now??

Posted by: Lawrence | Jul 23, 2007 5:13:31 PM

The human cost of global climate change will mostly be borne those poor countries unable to adjust their infrastructure to climate changes, many of whom will suffer more drought. The advanced nations of the West and Asia will be more likely to handle this. Of course, there will be a lot of hardship in the US anyway. I spend a lot of time at the shore and the rates of loss are alarming, even in my short memory.

So it's a moral imperative that we adopt lower-energy lifestyles, which also happen to be good for the bottom line. If you're not alarmed by the rise in your utility bills recently, than you are very rich indeed. I'm lucky. Living in NYC I take the subway to work everyday, saving huge amounts of money, plus I get to read.

Posted by: rob | Jul 23, 2007 5:14:21 PM

Sorry for the double post, but saw Tony's after I had posted. We won't survive much longer if we don't get our heads out of our collective butts and realize that our current lifestyle around the world will kill us off. Hopefully we'll do this soon, before some crazy with an idea that another country "might" have a nuke starts a war. Oh wait, that's already happened. Anyway. I too have hopes that humanity will survive long term and gain the ability to leave this planet and seek homes amoung the various other star systems we keep finding. Only time will tell.

Posted by: Lawrence | Jul 23, 2007 5:18:19 PM

Ever heard of quantum mechanics? It is all probabilities (not wave functions) that are observed. And of course they have been predicted up to the 10^-19 decimal place using "probabilities" (a la Q.E.D.). Those are PREDICTIONS using statistics. Of course your high school level math is not cutting it anymore.
Btw, which mutual fund company is beating the market every quarter using quantitative analysis? Ever heard of LTCM?? These monte carlo based simulations went from Physics (SCIENCE) to dummies at wall street and now to same caliber people in weather "science".

Of course, liberals will keep calling random "forecasting" a science without ever bothering to check if they can predict a damn thing in the future correctly (eg trajectory, frequency of hurricanes, El Nino). Have fun selling your idiotic propaganda.

Posted by: hysteriawatch | Jul 23, 2007 5:28:38 PM

I don't mean to sound like a crazy hippie from the 60's but wouldn't it be great if all the powerful countries would come together and spend their energy in space exploration rather than wars? We could be moving millions of people to other planets and help guarantee or existence as a species in the universe.

Posted by: tony | Jul 23, 2007 5:32:01 PM

Someone said ...
"In science, statistical models are used to FORECAST the likelihood of an event happening"
So, when you are typing your messages were you forecasting that the exact message would be entered the way you typed and then transmitted from your computer over to the server hosting this blog and appear to other users? You don't believe there are any certainties I take it as in math or computer languages or physics of computer hardware? Should we change newton's laws to Newton's Forecasts?

Posted by: bnl | Jul 23, 2007 5:40:31 PM

H:

Hm? My point seems to stand. The investment houses are making long bets on resource prices going up, and so far it's paid off pretty well for them. It's likely to continue as long as people want to eat, and obstructionists block any reasonable emissions regulations. I'm not BLAMING or attacking them, I'm no Marxist, I'm just saying we should have seen the writing on the wall.

And quantum mechanics? I suppose the mathematicians who do that stuff do in fact PREDICT what will happen if their model turns out one way or another, but it's pretty much paper to paper. Forecasting applies to the real world.

And don't try and put your opponents in a box. They're not offering to PREDICT, their offering a liklihood. They don't guarantee it, anymore than the insurance company guarantees you a long life when you buy a policy.

And the quants at the exchanges do verrrry well without your opinion of their skills, thank you very much.

Posted by: rob | Jul 23, 2007 5:41:29 PM

The weather in Arkansas has been cooler than normal and wet....we've not seen the rain to the extent that northern Texas and parts of Oklahoma saw, but we had a lot during June/July, the river is just now below flood stage after weeks of being over. We've gone over a week now without rain, but the temps are staying in the lower 90's, as compared to over 100 in past years during July. I think that our weather changes are proof of global warming to an extent, and I also think they are proof of evolution. Our planet is changing...it just doesn't change "overnight", which in God's terms may be 4 or 5 generations in people terms...who knows what His schedule for change is? Anyway, we should conserve, we should preserve, but we cannot change the fact that the world is evolving around us, we will just have to adapt or go like the dinosaurs did.

Posted by: ARSailorMom | Jul 23, 2007 5:45:27 PM

Fortunatley most Americans are not as complacent and fatalistic. As far as I'm concerned, the only thing in the way of halting this trend is adequate emisssions regulations, and the only things standing in the way of that are the President and the special interests (including a number of Democrats) in Congress.

Posted by: rob | Jul 23, 2007 5:52:43 PM

(I personally remain optimistic. I think there's plenty of opportunities to slow this down and eventually reverse it. People just have have to adjust their lifestyles. Did our forefathers have air conditioners? Shopping malls? SUVS? Nope....and they did pretty well.)

Posted by: rob | Jul 23, 2007 6:04:13 PM

You all sound like very intelligent people... but I think it is as simple as:

Human pollution is causing warming of the earth, which is causing the ice caps to melt, which is causing the oceans to flood with more water, which is causing the clouds to evaporate more water, which is causing more rain.

Right?

Posted by: holli | Jul 23, 2007 6:06:29 PM

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