Nov 3: Climate Change Seen Posing Risk to Food Supplies

November 3, 2013

http://www.nytimes.com/2013/11/02/science/earth/science-panel-warns-of-risks-to-food-supply-from-climate-change.html?smid=tw-nytimesscience&seid=auto&_r=0

Climate Change Seen Posing Risk to Food Supplies

Justin Gillis

Climate change will pose sharp risks to the world’s food supply in
coming decades, potentially undermining crop production and driving up
prices at a time when the demand for food is expected to soar,
scientists have found.

In a departure from an earlier assessment, the scientists concluded
that rising temperatures will have some beneficial effects on crops in
some places, but that globally they will make it harder for crops to
thrive — perhaps reducing production over all by as much as 2 percent
each decade for the rest of this century, compared with what it would
be without climate change.

And, the scientists say, they are already seeing the harmful effects
in some regions.

The warnings come in a leaked draft of a report under development by a
United Nations panel, the Intergovernmental Panel on Climate Change.
The document is not final and could change before it is released in
March.

The report also finds other sweeping impacts from climate change
already occurring across the planet, and warns that these are likely
to intensify as human emissions of greenhouse gases continue to rise.
The scientists describe a natural world in turmoil as plants and
animals colonize new areas to escape rising temperatures, and warn
that many could become extinct.

The warning on the food supply is the sharpest in tone the panel has
issued. Its previous report, in 2007, was more hopeful. While it did
warn of risks and potential losses in output, particularly in the
tropics, that report found that gains in production at higher
latitudes would most likely offset the losses and ensure an adequate
global supply.

The new tone reflects a large body of research in recent years that
has shown how sensitive crops appear to be to heat waves. The recent
work also challenges previous assumptions about how much food
production could increase in coming decades because of higher carbon
dioxide levels in the atmosphere. The gas, though it is the main
reason for global warming, also acts as a kind of fertilizer for
plants.

The Intergovernmental Panel on Climate Change is the principal
scientific body charged with reviewing and assessing climate science,
then issuing reports about the risks to the world’s governments. Its
main reports come out every five to six years. The group won the Nobel
Peace Prize, along with Al Gore, in 2007 for its efforts.

Hundreds of billions of dollars are being spent every year to reduce
emissions in response to past findings from the group, though many
analysts have said these efforts are so far inadequate to head off
drastic climatic changes later in the century.

On the food supply, the new report finds that benefits from global
warming may be seen in some areas, like northern lands that are now
marginal for food production. But it adds that over all, global
warming could reduce agricultural production by as much as 2 percent
each decade for the rest of this century.

During that period, demand is expected to rise as much as 14 percent
each decade, the report found, as the world population is projected to
grow to 9.6 billion in 2050, from 7.2 billion today, according to the
United Nations, and as many of those people in developing countries
acquire the money to eat richer diets.

Any shortfall would lead to rising food prices that would hit the
world’s poor hardest, as has already occurred from price increases of
recent years. Research has found that climate change, particularly
severe heat waves, was a factor in those price spikes.

The agricultural risks “are greatest for tropical countries, given
projected impacts that exceed adaptive capacity and higher poverty
rates compared with temperate regions,” the draft report finds.

If the report proves to be correct about the effect on crops from
climate change, global food demand might have to be met — if it can be
met — by putting new land into production. That could entail chopping
down large areas of forest, an action that would only accelerate
climate change by sending substantial amounts of carbon dioxide into
the air from the destruction of trees.

The report finds that efforts to adapt to climate change have already
begun in many countries. President Obama signed an executive order on
Friday to step up such efforts in the United States. But these efforts
remain inadequate compared with the risks, the report says, and far
more intensive — and expensive — adaptation plans are likely to be
required in the future.

The document also finds that it is not too late for cuts in emissions
to have a strong impact on the future risks of climate change, though
the costs would be incurred in the next few decades and the main
benefits would probably be seen in the late 21st century and beyond.

The leak of the new draft occurred on a blog hostile to the
intergovernmental panel. In a brief interview, a spokesman for the
panel, Jonathan Lynn, did not dispute the authenticity of the
document.

“It’s a work in progress,” Mr. Lynn said. “It’s likely to change.”

Several scientists involved in drafting the document declined on
Friday to speak publicly about it. In the Internet era, the group’s
efforts to keep its drafts secret are proving to be a failure, and
some of the scientists involved have called for a drafting process
open to the public.

A report about the physical science of climate change leaked in
August, then underwent only modest changes before its final release in
Stockholm in late September. The new report covers the impact of
climate change, efforts to adapt to it, and the vulnerability of human
and natural systems.

A third report, analyzing potential ways to limit the rise of
greenhouse gases, is due for release in Berlin in April.