Global Warming has Already Changed World’s Rainfall Patterns: Study

PARIS — A study has yielded the first confirmation that global warming is already affecting world’s rainfall patterns, bringing more precipitation to northern Europe, Canada and northern Russia but less to swathes of sub-Saharan Africa, southern India and Southeast Asia.

The changes “may have already had significant effects on ecosystems, agriculture and human regions that are sensitive to changes in precipitation, such as the Sahel,” warns the paper, released on Monday by Nature, the British science journal.

Scientists have long said that global warming is bound to interfere with snow and rainfall patterns, because air and sea temperatures and sea-level atmospheric pressure — the underlying forces behind these patterns — are already changing.

But, until now, evidence for declaring that the interference is already happening existed anecdotally or in computer models, rather than from observation.

One problem for researchers has been a lack of accurate, long-term rainfall data from around the world that would enable them to distinguish between regional or cyclical shifts in rainfall.

Francis Zwiers, a scientists with Environment Canada, Toronto, found a way around these problems by using two data-sets of global rainfall pattern beginning, conservatively, in 1925 and ending in 1999.

They compared these figures with 14 powerful computer models that simulate the world’s climate system, and found a remarkably close fit.

Over the 75-year period under study, global warming “contributed significantly” to increases in precipitation in the Northern Hemisphere’s mid-latitudes, a region between 40 and 70 degrees north, they say.

In contrast, the Northern Hemisphere’s tropics and subtropics, a region spanning from the equator to 30 degrees latitude north became drier.

And the Southern Hemisphere’s tropics (equator to 30 degrees latitude south) became wetter.

The study looked at annual average rainfall on the land, not at sea. In addition, it did not look at extreme weather events — episodes of drought and flooding — whose frequency and severity are also seen as likely to increase as a result of global warming.

The investigation is published by Nature on Thursday.

Previous work in the past few years has highlighted the loss of alpine glaciers and snow cover and the retreat of Arctic permafrost.

These were interpreted by the UN’s Intergovernmental Panel on Climate Change (IPCC), in a landmark report published this year, as confirmation that global warming has already started to affect parts of the climate system.

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16 Comments so far

sigma July 23rd, 2007 5:56 pm

The Sahel has been drying up for 400 years. They need to correct for macro patterns in the earth’s orbit and solar activity to make this meaningful.

thaddeusstephens July 23rd, 2007 7:00 pm

Hello sigma:
“The Sahel has been drying up” for how long?
Do you have any citations to share that give us some context of your statement?
The Sahel is indeed subject to the forces of desertification, the area has been worked over by horticulturalists, farmers, and industrialists for many centuries. You have not shown how this is relevant to the discussion in the article.
The solar output (your, solar activity refers to this phenomena, I assume)has been fairly consistent for long periods of time, no one that I can find claims that there has been any significant variation in solar output for the last 100 years or perhaps longer-5 or 600 hundred years or possibly even for the last several hundred thousand years.
This website:
http://vathena.arc.nasa.gov/curric/space/solterr/output.html
shows the solar output to be fairly constant to a very fine degree of measurement, the basic units are thousands of watts per square meter.
There was a period, known as the “Little Ice Age:
http://www.ngdc.noaa.gov/paleo/ctl/resource1000.html
where solar output appears to be one of several significant factors-others being the deforestation of Europe that was going on consistently from the early 14th century. Forests act as rainfall buffers (kind of like a the human kidney system is a buffering system for water ), there removal could conceivably have direct consequences for the climate.
The earth’s orbit is consistent enough, and much is known on this topic.To make the suggestion that variations in its eccentricity could cause climate change is very speculative to say the least and needs to be backed up by some more information before I would give credence to such a statement.
I am wondering at this point if you are sincere or if you have some political ax to grind.

ellydozer July 23rd, 2007 9:29 pm

ha-ha-HA!!!! take THAT!- nonbeliever!!!

BugsBBunny III July 24th, 2007 1:07 am

A problem we face is the difficulty of proving scientifically that the evidence for global warming is caused by this or that specific reason. However, it is the science that is inadequate to the task of showing the evidence is due to man’s activities, not that the evidence doesn’t actually exist. There are those who say global warming doesn’t exist because science can’t yet quantify a direct cause and effect process and show that these are direct linked to man’s activities. Had we begun studying the effects of man’s activities on the enviornment a century ago, then the scientific data and studies would be there as proof but we didn’t. We waited till we smelled smoke and still some say you can’t prove that smoke means that there is a fire. One can only imagine that such people who laugh and say you can’t prove global warming are the kind of people when they smell smoke, refuse to admit the need to call the fire dept. until they actually see the fire for themselves. But by then of course, it may be too late.

commonman03 July 24th, 2007 1:58 am

BugsBBunny III

The vast vast majority of scientists are very clear that the evidence is irrefutable that man is the primary cause of global warming. The only doubt exists in the media, or the 1% of scientist bought and paid for by industry, and those who believe the media (okay … and the Bush Administration). But you have the right idea. It may already be too late.

sigma July 24th, 2007 8:17 am

thaddeusstephes- ” I am wondering at this point if you are sincere or have a political ax to grind” . I myself have no such political ax to grind, apparently the same can’t be said for others on this post. Everyone that asks a question is not on Bush’s payroll. I don’t think that there is really any question that co2 levels have risen over the last 150 years due to man’s activity. At the same time, something else must have caused the wide shifts in weather patterns recorded before the industrial era, like the little ice age and the medieval warming period that allowed the norse to inhabit Greenland and sea levels to rise. This
has been attributed to increased solar activity and shifts in the earth orbit and slant of it’s axis. Is this true? who knows? But something caused it and I think more research is needed.

In the last 50 years scientific consensus on the direction and causes of global temperatures has shifted back and forth. I remember back in the 70’s, while I was in high school, my science teacher just KNEW that global COOLING was happening and that another ice age was approaching. He backed this up with lots of scientific consensus research and became very angry when I questioned him about it. I also remember that when, in the 1980’s, it was suggested by the president that cows contributed to the accumulation of greenhouse gasses, it was universally derided by the scientific community. Now I read that a link with cows and greenhouse gasses is a newly discovered FACT.
As far as the Sahel is concerned, desertification and shifting rain patterns have, as far as I know, been an ongoing problem for this area for this area for at least 400-500 years. It contributed to the fall of some of the interior african empires in the 16th and 17th century. Mungo Park, the explorer, reported the effects and the abandoned settlements at the last part of the 18th century.

Now scientists are saying that, even without any increase in greenhouse gasses, the earths temperature is going to continue to rise. I think someone ought to be thinking about what we are going to do about the effects of our warming planet.

Myself, I’m not a climatologist. However, I didn’t give up my rights to question the consensus in high school and I have no intention of doing it now. If that makes me unpopular in some forums, I don’t really care.

WmC July 24th, 2007 8:29 am

The burden of proof should now be on the denial crowd (like sigma above.)

They need:
1) To prove that the measures needed to counter global warming will have a serious negative economic impact.

2) To prove that these measures (reforestation, reducing air and water pollution, decreasing dependence on foreign oil) are not worth doing for other reasons; i.e. even if global warming is not occurring.

sigma July 24th, 2007 9:23 am

WmC - Now I’m in the “denial” crowd. Does that mean that I don’t get to sit at the “popular kids” table?

MrMark July 24th, 2007 9:34 am

Denial does seem a bit strong a term for our friend sigma… Skepicism is of course healthy, but let us not forget we are talking about an article in one of the most prestigious peer reviewed scientific journals on the planet…. using my superpowers, i obtained a copy of the article “Detection of human influence on twentieth century precipitation trends”, and i think the following passage is relevant:

_We show that anthropogenic forcing 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. We estimate that anthropogenic forcing contributed significantly to observed increases in precipitation in the Northern Hemisphere mid-latitudes, drying in the Northern Hemisphere subtropic and tropics, and moistening in the Southern Hemisphere subtropics and deep tropics. The observed changes, which are larger than estimated from model simulations, may have already had significant effects on ecosystems, agriculture and human health in regions that are sensitive to changes in precipitation, such as the Sahel._

I think a passage like that, published in Nature let’s not forget, pretty much rules out solar activity or macro patterns in the earths orbit as a significant cause or climate change. Anything coming from cows would be included in human activity as well. they certainly wouldn’t be here if we weren’t farming them! This paper is yet anothr nail in the coffin for the climate change skeptics… Bottom line, I don’t think this article should be so easily dismissed sigma…

sigma July 24th, 2007 9:53 am

Mr. Mark- thank you for the informative response. Again, I think the question now is, “We know this is happening, how can we help the people affected?” My friends in Australia tell me that they are going through the worst drought in their recorded history. Britain is underwater. I think more research needs to be done, while working towards mitagating the effects in the areas affected. I have a friend in the sahel right now who is trying to help them tap into the underground aquifiers. This is the type of practical help that is needed, in my opinion.

Demerara July 24th, 2007 10:54 am

It is better to err on the side of reducing global warming than to wait for more proof on the source of global warming. There is a lot to gain in jobs, changes in lifestyle, being more caring to the planet than to support big business to continue ‘as usual’. It only takes a rise of a few more degrees before we enter into a catastrophic cycle without return.

badgersouth July 24th, 2007 12:36 pm

Here’s another example of how climate change is negatively impacting Africa.

Global Warming Threatens Coffee Collapse in Uganda
Alexis Okeowo in Nsangi, Uganda
for National Geographic News

July 24, 2007

Things are getting hot for coffee farmers in Uganda—a little too hot.

Growers say global warming is already cutting into coffee harvests, the country’s biggest export.

And a new report warns that even a slight increase in temperature could wipe out Uganda’s entire coffee crop, which brings in more than half of the East African country’s revenue.

“Climate change has affected coffee production already,” said Philip Gitao, executive director of the East African Fine Coffees Association.

To access the entire article, go to: http://news.nationalgeographic.com/news/index.html

jdpst44 July 24th, 2007 1:22 pm

Sigma,

You know you want to be popular. You know you want to join the kids at the party. The fence is not a comfortable place to be. It’s okay to want some cake.

Antidote July 24th, 2007 4:20 pm

…

ubrew12 July 24th, 2007 10:42 pm

sigma said: “my science teacher just KNEW that global COOLING was happening and that another ice age was approaching”

Global dimming (aka cooling) did happen in the 70s. The Clean Air Act took aerosols out of the atmosphere and relieved the danger. The effect of aerosols is still so strong that if all air flights were to be cancelled, air temperatures would rise 1 C (which is exactly what happened in the 2 days after 9-11).

Climatologists think that about 25-35% of current warming is due to a rise in the solar constant (solar insolation) over the last 30 years or so, which would also be affecting Mars, etc. The rest is Global Warming.

You don’t get to say that CO2 is a major factor in the ‘greenhouse effect’ and then turn around and say a 50% rise in CO2 is not going to have an affect on climate. The fact is, without CO2 levels where they historically have been, we’d all be locked in an ice age far worse than any that has been historically measured. That is NOT under dispute. What apparently IS under dispute, at least with some people, is that you can raise CO2 levels by 50% and NOT see a change in climate. That argument is absurd on its face, and always has been.

Though it does make you look discerning and not easily flim-flammed to say so.

sigma July 25th, 2007 9:17 am

Ubrew - Sorry, I never said that man made pollution has not caused the increase in greenhouse gases. Also never said a rise in these gases aren’t going to have the effect of warming the earth. I simply pointed out that something else must have been at work during the well-documented periods of pre-industrial warming.

As far as my 70’s science teachers assertion that we were headed for another ice age due to global cooling being averted because of the clean air act, nice try but no dice. The Montreal accords to reduce ozone depleting chemicals was not implemented for reduction until 1994. Since the current warming trend began before 1980, one couldn’t have anything to do with the other. Mr. Sheffield (the science teacher) was wrong, plain and simple.
As far as absurd arguments go, your argument that temperatures went up 1C in the two days after 9/11 because of the grounding of American aircraft would be a neat trick, considering that the TOTAL warming has been around 4/10s of one percent Centigrade in the 27 YEARS since 1980. Wow, I get to look discerning again.

Once more, if we know that the earth, according to most scientist, is in a warming trend even if greenhouse gases stay the same what are we going to do about the people affected? My family has been in the business of developing and installing scrubbers and filters in industrial plants to reduce these harmful emissions by thousands of tons since 1968. What have you done?

sigma July 23rd, 2007 5:56 pm

The Sahel has been drying up for 400 years. They need to correct for macro patterns in the earth’s orbit and solar activity to make this meaningful.
thaddeusstephens July 23rd, 2007 7:00 pm

Hello sigma:
“The Sahel has been drying up” for how long?
Do you have any citations to share that give us some context of your statement?
The Sahel is indeed subject to the forces of desertification, the area has been worked over by horticulturalists, farmers, and industrialists for many centuries. You have not shown how this is relevant to the discussion in the article.
The solar output (your, solar activity refers to this phenomena, I assume)has been fairly consistent for long periods of time, no one that I can find claims that there has been any significant variation in solar output for the last 100 years or perhaps longer-5 or 600 hundred years or possibly even for the last several hundred thousand years.
This website:
http://vathena.arc.nasa.gov/curric/space/solterr/output.html
shows the solar output to be fairly constant to a very fine degree of measurement, the basic units are thousands of watts per square meter.
There was a period, known as the “Little Ice Age:
http://www.ngdc.noaa.gov/paleo/ctl/resource1000.html
where solar output appears to be one of several significant factors-others being the deforestation of Europe that was going on consistently from the early 14th century. Forests act as rainfall buffers (kind of like a the human kidney system is a buffering system for water ), there removal could conceivably have direct consequences for the climate.
The earth’s orbit is consistent enough, and much is known on this topic.To make the suggestion that variations in its eccentricity could cause climate change is very speculative to say the least and needs to be backed up by some more information before I would give credence to such a statement.
I am wondering at this point if you are sincere or if you have some political ax to grind.
ellydozer July 23rd, 2007 9:29 pm

ha-ha-HA!!!! take THAT!- nonbeliever!!!
BugsBBunny III July 24th, 2007 1:07 am

A problem we face is the difficulty of proving scientifically that the evidence for global warming is caused by this or that specific reason. However, it is the science that is inadequate to the task of showing the evidence is due to man’s activities, not that the evidence doesn’t actually exist. There are those who say global warming doesn’t exist because science can’t yet quantify a direct cause and effect process and show that these are direct linked to man’s activities. Had we begun studying the effects of man’s activities on the enviornment a century ago, then the scientific data and studies would be there as proof but we didn’t. We waited till we smelled smoke and still some say you can’t prove that smoke means that there is a fire. One can only imagine that such people who laugh and say you can’t prove global warming are the kind of people when they smell smoke, refuse to admit the need to call the fire dept. until they actually see the fire for themselves. But by then of course, it may be too late.
commonman03 July 24th, 2007 1:58 am

BugsBBunny III

The vast vast majority of scientists are very clear that the evidence is irrefutable that man is the primary cause of global warming. The only doubt exists in the media, or the 1% of scientist bought and paid for by industry, and those who believe the media (okay … and the Bush Administration). But you have the right idea. It may already be too late.
sigma July 24th, 2007 8:17 am

thaddeusstephes- ” I am wondering at this point if you are sincere or have a political ax to grind” . I myself have no such political ax to grind, apparently the same can’t be said for others on this post. Everyone that asks a question is not on Bush’s payroll. I don’t think that there is really any question that co2 levels have risen over the last 150 years due to man’s activity. At the same time, something else must have caused the wide shifts in weather patterns recorded before the industrial era, like the little ice age and the medieval warming period that allowed the norse to inhabit Greenland and sea levels to rise. This
has been attributed to increased solar activity and shifts in the earth orbit and slant of it’s axis. Is this true? who knows? But something caused it and I think more research is needed.

In the last 50 years scientific consensus on the direction and causes of global temperatures has shifted back and forth. I remember back in the 70’s, while I was in high school, my science teacher just KNEW that global COOLING was happening and that another ice age was approaching. He backed this up with lots of scientific consensus research and became very angry when I questioned him about it. I also remember that when, in the 1980’s, it was suggested by the president that cows contributed to the accumulation of greenhouse gasses, it was universally derided by the scientific community. Now I read that a link with cows and greenhouse gasses is a newly discovered FACT.
As far as the Sahel is concerned, desertification and shifting rain patterns have, as far as I know, been an ongoing problem for this area for this area for at least 400-500 years. It contributed to the fall of some of the interior african empires in the 16th and 17th century. Mungo Park, the explorer, reported the effects and the abandoned settlements at the last part of the 18th century.

Now scientists are saying that, even without any increase in greenhouse gasses, the earths temperature is going to continue to rise. I think someone ought to be thinking about what we are going to do about the effects of our warming planet.

Myself, I’m not a climatologist. However, I didn’t give up my rights to question the consensus in high school and I have no intention of doing it now. If that makes me unpopular in some forums, I don’t really care.
WmC July 24th, 2007 8:29 am

The burden of proof should now be on the denial crowd (like sigma above.)

They need:
1) To prove that the measures needed to counter global warming will have a serious negative economic impact.

2) To prove that these measures (reforestation, reducing air and water pollution, decreasing dependence on foreign oil) are not worth doing for other reasons; i.e. even if global warming is not occurring.
sigma July 24th, 2007 9:23 am

WmC - Now I’m in the “denial” crowd. Does that mean that I don’t get to sit at the “popular kids” table?
MrMark July 24th, 2007 9:34 am

Denial does seem a bit strong a term for our friend sigma… Skepicism is of course healthy, but let us not forget we are talking about an article in one of the most prestigious peer reviewed scientific journals on the planet…. using my superpowers, i obtained a copy of the article “Detection of human influence on twentieth century precipitation trends”, and i think the following passage is relevant:

_We show that anthropogenic forcing 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. We estimate that anthropogenic forcing contributed significantly to observed increases in precipitation in the Northern Hemisphere mid-latitudes, drying in the Northern Hemisphere subtropic and tropics, and moistening in the Southern Hemisphere subtropics and deep tropics. The observed changes, which are larger than estimated from model simulations, may have already had significant effects on ecosystems, agriculture and human health in regions that are sensitive to changes in precipitation, such as the Sahel._

I think a passage like that, published in Nature let’s not forget, pretty much rules out solar activity or macro patterns in the earths orbit as a significant cause or climate change. Anything coming from cows would be included in human activity as well. they certainly wouldn’t be here if we weren’t farming them! This paper is yet anothr nail in the coffin for the climate change skeptics… Bottom line, I don’t think this article should be so easily dismissed sigma…
sigma July 24th, 2007 9:53 am

Mr. Mark- thank you for the informative response. Again, I think the question now is, “We know this is happening, how can we help the people affected?” My friends in Australia tell me that they are going through the worst drought in their recorded history. Britain is underwater. I think more research needs to be done, while working towards mitagating the effects in the areas affected. I have a friend in the sahel right now who is trying to help them tap into the underground aquifiers. This is the type of practical help that is needed, in my opinion.
Demerara July 24th, 2007 10:54 am

It is better to err on the side of reducing global warming than to wait for more proof on the source of global warming. There is a lot to gain in jobs, changes in lifestyle, being more caring to the planet than to support big business to continue ‘as usual’. It only takes a rise of a few more degrees before we enter into a catastrophic cycle without return.
badgersouth July 24th, 2007 12:36 pm

Here’s another example of how climate change is negatively impacting Africa.

Global Warming Threatens Coffee Collapse in Uganda
Alexis Okeowo in Nsangi, Uganda
for National Geographic News

July 24, 2007

Things are getting hot for coffee farmers in Uganda—a little too hot.

Growers say global warming is already cutting into coffee harvests, the country’s biggest export.

And a new report warns that even a slight increase in temperature could wipe out Uganda’s entire coffee crop, which brings in more than half of the East African country’s revenue.

“Climate change has affected coffee production already,” said Philip Gitao, executive director of the East African Fine Coffees Association.

To access the entire article, go to: http://news.nationalgeographic.com/news/index.html
jdpst44 July 24th, 2007 1:22 pm

Sigma,

You know you want to be popular. You know you want to join the kids at the party. The fence is not a comfortable place to be. It’s okay to want some cake.
Antidote July 24th, 2007 4:20 pm

…
ubrew12 July 24th, 2007 10:42 pm

sigma said: “my science teacher just KNEW that global COOLING was happening and that another ice age was approaching”

Global dimming (aka cooling) did happen in the 70s. The Clean Air Act took aerosols out of the atmosphere and relieved the danger. The effect of aerosols is still so strong that if all air flights were to be cancelled, air temperatures would rise 1 C (which is exactly what happened in the 2 days after 9-11).

Climatologists think that about 25-35% of current warming is due to a rise in the solar constant (solar insolation) over the last 30 years or so, which would also be affecting Mars, etc. The rest is Global Warming.

You don’t get to say that CO2 is a major factor in the ‘greenhouse effect’ and then turn around and say a 50% rise in CO2 is not going to have an affect on climate. The fact is, without CO2 levels where they historically have been, we’d all be locked in an ice age far worse than any that has been historically measured. That is NOT under dispute. What apparently IS under dispute, at least with some people, is that you can raise CO2 levels by 50% and NOT see a change in climate. That argument is absurd on its face, and always has been.

Though it does make you look discerning and not easily flim-flammed to say so.
sigma July 25th, 2007 9:17 am

Ubrew - Sorry, I never said that man made pollution has not caused the increase in greenhouse gases. Also never said a rise in these gases aren’t going to have the effect of warming the earth. I simply pointed out that something else must have been at work during the well-documented periods of pre-industrial warming.

As far as my 70’s science teachers assertion that we were headed for another ice age due to global cooling being averted because of the clean air act, nice try but no dice. The Montreal accords to reduce ozone depleting chemicals was not implemented for reduction until 1994. Since the current warming trend began before 1980, one couldn’t have anything to do with the other. Mr. Sheffield (the science teacher) was wrong, plain and simple.
As far as absurd arguments go, your argument that temperatures went up 1C in the two days after 9/11 because of the grounding of American aircraft would be a neat trick, considering that the TOTAL warming has been around 4/10s of one percent Centigrade in the 27 YEARS since 1980. Wow, I get to look discerning again.

Once more, if we know that the earth, according to most scientist, is in a warming trend even if greenhouse gases stay the same what are we going to do about the people affected? My family has been in the business of developing and installing scrubbers and filters in industrial plants to reduce these harmful emissions by thousands of tons since 1968. What have you done?

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