Nature Climate Change - Expect Near-Doubling Of Planet's Arid Lands By Century's End

[hatrack]

LONDON ? If global greenhouse gas emissions continue to rise, the outlook for at least half the inhabited planet looks arid. By 2100, according to new research, at least half ? and perhaps as much as 56% ? of the land surface of the planet will be classified as dryland.

Dryland, to a geographer, is not desert: it is terrain on which rain certainly falls, but rainfall is balanced by evaporation and transpiration through plant tissues. That is, dryland offers a precarious living to a sparse population. It doesn’t take much – overgrazing, erosion, ambitious cropping ? to tip the balance and turn the land into desert. Right now, 38% of humanity makes a living on the drylands.

So the report in Nature Climate Change by atmospheric scientist Jianping Huang and colleagues at Lanzhou University in China that under global warming scenarios, drylands are to expand is very bad news for those who are already among the poorest in the world.

That is because 78% of expansion of drylands – and 50% of the planet’s population growth – will occur in the developing countries. Climate scientists have already predicted that, in a warming world, arid regions are likely to get even less rain, while humid ones could be at greater risk of flooding.

EDIT

http://climatechangepsychology.blogspot.com/2015/11/global-warming-increasing-aridity-and.html

[muriel_volestrangler]

1. No, it's not a near doubling of dryland

It's an increase of either 11%, or 23% (there are 2 scenarios). In terms of the total land areas, that's up to either 50% or 56% - which are both consistent with the baseline (1961-90) figure for dryland being about 45%.

Here's the letter to Nature Climate Change:

Drylands are home to more than 38% of the total global population and are one of the most sensitive areas to climate change and human activities. Projecting the areal change in drylands is essential for taking early action to prevent the aggravation of global desertification. However, dryland expansion has been underestimated in the Fifth Coupled Model Intercomparison Project (CMIP5) simulations considering the past 58 years (1948–2005). Here, using historical data to bias-correct CMIP5 projections, we show an increase in dryland expansion rate resulting in the drylands covering half of the global land surface by the end of this century. Dryland area, projected under representative concentration pathways (RCPs) RCP8.5 and RCP4.5, will increase by 23% and 11%, respectively, relative to 1961–1990 baseline, equalling 56% and 50%, respectively, of total land surface. Such an expansion of drylands would lead to reduced carbon sequestration and enhanced regional warming, resulting in warming trends over the present drylands that are double those over humid regions. The increasing aridity, enhanced warming and rapidly growing human population will exacerbate the risk of land degradation and desertification in the near future in the drylands of developing countries, where 78% of dryland expansion and 50% of the population growth will occur under RCP8.5.



http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate2837.html