Heat, Not Just Rainfall, Plays into New Projections
Increasing heat is expected to extend dry conditions to far more farmland and cities by the end of the century than changes in rainfall alone, says a new study. Much of the concern about future drought under global warming has focused on rainfall projections, but higher evaporation rates may also play an important role as warmer temperatures wring more moisture from the soil, even in some places where rainfall is forecasted to increase, say the researchers.
The study is one of the first to use the latest climate simulations to model the effects of both changing rainfall and evaporation rates on future drought. Published this month in the journal Climate Dynamics, the study estimates that 12 percent of land will be subject to drought by 2100 through rainfall changes alone; but the drying will spread to 30 percent of land if higher evaporation rates from the added energy and humidity in the atmosphere is considered.
An increase in evaporative drying means that even regions expected to get more rain, including important wheat, corn and rice belts in the western United States and southeastern China, will be at risk of drought. The study excludes Antarctica.
“We know from basic physics that warmer temperatures will help to dry things out,” said the study’s lead author, Benjamin Cook, a climate scientist with joint appointments at Columbia University’s Lamont-Doherty Earth Observatory and the NASA Goddard Institute for Space Studies. “Even if precipitation changes in the future are uncertain, there are good reasons to be concerned about water resources.”
In its latest climate report, the International Panel on Climate Change (IPCC) warns that soil moisture is expected to decline globally and that already dry regions will be at greater risk of agricultural drought. The IPCC also predicts a strong chance of soil moisture drying in the Mediterranean, southwestern United States and southern African regions, consistent with the Climate Dynamics study.
Using two drought metric formulations, the study authors analyze projections of both rainfall and evaporative demand from the collection of climate model simulations completed for the IPCC’s 2013 climate report. Both metrics agree that increased evaporative drying will probably tip marginally wet regions at mid-latitudes like the U.S. Great Plains and a swath of southeastern China into aridity. If precipitation were the only consideration, these great agricultural centers would not be considered at risk of drought. The researchers also say that dry zones in Central America, the Amazon and southern Africa will grow larger. In Europe, the summer aridity of Greece, Turkey, Italy and Spain is expected to extend farther north into continental Europe.
“For agriculture, the moisture balance in the soil is what really matters,” said study coauthor Jason Smerdon, a climate scientist at Lamont-Doherty. “If rain increases slightly but temperatures also increase, drought is a potential consequence.”
Today, while bad weather periodically lowers crop yields in some places, other regions are typically able to compensate to avert food shortages. In the warmer weather of the future, however, crops in multiple regions could wither simultaneously, the authors suggest. “Food-price shocks could become far more common,” said study coauthor Richard Seager, a climate scientist at Lamont-Doherty. Large cities, especially in arid regions, will need to carefully manage their water supplies, he added.
The study builds on an emerging body of research looking at how evaporative demand influences hydroclimate. “It confirms something we’ve suspected for a long time,” said Toby Ault, a climate scientist at Cornell University, who was not involved in the study. “Temperature alone can make drought more widespread. Studies like this give us a few new powerful tools to plan for and adapt to climate change.”
Rainfall changes do not tell the whole story, agrees University of New South Wales researcher Steven Sherwood, in a recent Perspectives piece in the leading journal Science. “Many regions will get more rain, but it appears that few will get enough to keep pace with the growing evaporative demand.”
The authors have made all their data and calculations public available on a supplementary website.
Discover more from Watts Up With That?
Subscribe to get the latest posts sent to your email.
The world’s surface has warmed since the LIA. We have had the ‘fastest rate of warming evahhhhh!’ and ‘unprecedented heat and all that!. So what have we OBSERVED during THIS ‘experiment’?
It must be April’s fool as even the CAGW are not so silly. Above article:
“the study estimates that 12 percent of land will be subject to drought by 2100 through rainfall changes alone; but the drying will spread to 30 percent of land if higher evaporation rates from the added energy and humidity in the atmosphere is considered.”
Vs:
“Deserts actually make up 33%, or 1/3rd of the land’s surface area.”
Read more: http://www.universetoday.com/65639/what-percentage-of-the-earths-land-surface-is-desert/#ixzz2xd89BGSQ
So if drying spreads to 30% land, we would less desert area in future, than we have currently.
And of course with irrigation, deserts can be good places to grow crops- ie, California.
Deserts aren’t problem but rather it is idiots that are against building dams which is the problem.
When glaciers covered much of the Northern Hemisphere during the last ice age (approximately 15 thousand years ago) areas of desert were larger and drier than they are today. This makes sense, since much more or the earth’s water supply was locked up in the ice sheets. During the Holocene optimum (approximately 5000 years ago) when the earth’s climate was warmer than today, large parts of what is now the Sahara desert was covered with shallow lakes and grasslands. That also makes sense, since the polar areas were covered by less ice than today, which means there was more water unlocked and circulating in the atmosphere. So, here we have two data points — much colder in the past, more desert; warmer in the past, less desert. You’d think by this point that even your typical science journalist with even a nodding acquaintance to what the earth’s climate history was over the last 15000 years could see how mistaken this study is.
Every day is April Fools day with the alarmists.
“According to NASA, ‘Between 1982 and 1999, 25 percent of the Earth’s vegetated area experienced increasing plant productivity—a total increase of about 6 percent,’ says Ramakrishna Nemani, the [NASA] study’s lead scientist.” — from a 2003 NASA article, “Global Garden Gets Greener”
What happened between 1982 and 1999? Why, just about all of the warming we’ve experienced to this point. So while — yet again — actual observations show one thing, the warmies get out a model that shows the exact opposite and claim it as the truth.
Do they ever look out the window to see if it’s raining or not?
They will need to explain how the math works here. It’s usually my default position because it often explains the basic facts and logic better than anything else.
In this case, water vapor cycles through the atmosphere each 9 days. If water evaporates from a surface somewhere, on average it will rain out somewhere else 9 days later.
The climate models project that warming will increase water vapor levels by 23% by the year 2100. That means rainfall is also going to increase by 23% (or maybe only 22% if the 9 days changes to 9.1 days in a warmer world).
If rainfall is going to increase by 22%, how can any place on the planet end up dryer? I’m sure one can contort themselves into thinking there will be more droughts but it is not accurate. It is completely inconsistent with what the theory is about.
The last time the Earth was 1.0 degree warmer, the Saharra had trees and lakes. The last time it was 2.0C warmer, 10 million years ago, there was so much rainfall, that the entire planet was forested with virtually no desert or grassland.
It’s not a real science. It’s a religious-type movement.
all these cries of doom and yet one of the biggest problems in the west is obesity and wastage of food thrown away and for the future a population that will hit 9 billion half or this being African, there stories of doom are so disjointed.
There is nothing today that has not happened in the last 2000 years but lots has happened that has not happened in the last 100 years.
No1 100 -150 year droughts over the last 1000 years.
The story carefully states that the study excluded Antarctica where, as we all know, there will be vast new areas of virgin farmland.
I suspect some Aussies staked out a bunch last Christmas.
But, but I thought more moisture in the air was the big positive feedback that turned the extra CO2 GH effect into the CAGW supercharged death killer gas mix.
This is just getting toooo confusing.
Its like Occupy Global Warming. Lots of light and movement but no science just the science communications industry twerking for the msm.
… Warming Climate May Spread Drying to a Third of Earth, Says Study
Warming – WHAT WARMING!!??
Seeing single digit temps in the Dakotas this morning, and teens in Minnesota, and Montana, and as far south as Nebraska! … Warming my you-know-what!
.
By 2100 the only thing certain is that people will look back at all this and laugh at how silly we were.
People imagined droughts spreading around the world, crops withering while temperatures soar, they will laugh. As it turned out, it was the exact opposite. A slightly warmer world has given us a little more precipitation and together with the higher co2 concentrations, arid regions have greened, vegetation is abundant and crop yields have continued to increase.
Worth seeing what is really going on with the Sun, because it is unusual in the scale of the known measurements.
http://oi58.tinypic.com/2q0o7fa.jpg
AFRICA, warmth and drying?
Their dynamic inter-cell interactions are screwed up. They have their pressure gradients and flows backwards. Water content in the air is static and an averaged number used thus the model is not dynamic to the heat and water relationship.
This is nothing more than a “tweaked” linear model. The model appears to be intentionally designed to go upward, period!
One word sums it up; Garbage!
re: jones says April 1, 2014 at 1:10 am
… “Here come de heap big warmy. Bigtime warmy warmy. Is big big hot. Plenty big warm burny hot. Hot! Hot hot! … ”
Very funny piece; thanks for sharing!
.
These arnt studies. You should stop calling them that. Scientific studies require empirical evidence. These are more akin to fictional short-stories.
Hmm… 70% of the Earth is covered by water. That is more than 2 thirds! If the remainder dries up we are doomed!
As the magnetic current solar activity correlates with forecasts NASA? Where are the paralyzing magnetic storms?
http://www.swpc.noaa.gov/SolarCycle/Ap.gif
AUSTRALIA
Such was the magnetic activity in September 2005.
http://www.swpc.noaa.gov/aviation/index_files/20050915_kp.gif
In the “silver lining” dept.:
I started playing golf in 2004 and as I became aware of the El Nino cycles of the 1990’s I wished I’d started a decade earlier. Having seen the last couple of years and the projections based on observations I’m thinking “Dang! I’ll be playing golf – outside – about two months of the year and driving my motorcycle maybe three!”
But this report, oh sure it’s April Fool’s day and what an April Fool’s day it is in Halifax with freezing rain, ice and snow…, but this report gives me hope. A vapor perhaps, ephemeral maybe, but I could be playing golf all year round – with waaay bigger bunkers mind you – but hey that little white ball doesn’t care and neither will I.
Okay, back to reality and maybe a second morning cup of coffee. …as you were.
“the drying will spread to 30 percent of land if higher evaporation rates from the added energy and humidity in the atmosphere is considered.”???
Pardon my physics, but HIGHER humidity means LOWER evaporation rates!
re: ren says April 1, 2014 at 5:01 am
… Where are the paralyzing magnetic storms?
Do you work in the power generation, transmission or distribution industry?
.
Whoever chose the cornfield picture at the top of this post obviously is following the Al Gore policy of threat-by-carefully-chosen-photo but is obviously totally unable to tell the difference between a cornfield recently harvested and a cornfield ravaged by drought.
“It confirms something we’ve suspected for a long time,”
That the answer came before the model is no surprise but “confirms,” how does that work?