I believe we might have made a mistake: a mistake whose consequences,
if I am right, would be hard to overstate. I think the forecasts for
world food production could be entirely wrong. Food prices are rising
again, partly because of the damage done to crops in the northern
hemisphere by ferocious weather. In the US, Russia and Ukraine, grain
crops were clobbered by remarkable droughts. In parts of northern
Europe, such as the UK, they were pummeled by endless rain.
Even so, this is not, as a report in the Guardian claimed last week,
"one of the worst global harvests in years". It's one of the best.
World grain production last year was the highest on record; this year's
crop is just 2.6% smaller. The problem is that, thanks to the combination of a rising population and the immoral diversion of so much grain into animal feed and biofuels, a new record must be set every year. Though 2012's is the third biggest global harvest in history (after 2011 and 2008), this is also a year of food deficit, in which we will consume 28m tonnes more grain than farmers produced. If 2013's harvest does not establish a new world record, the poor are in serious trouble.
So
the question of how climate change might alter food production could
not be more significant. It is also extremely hard to resolve, and
relies on such daunting instruments as "multinomial endogenous switching regression models".
The problem is that there are so many factors involved. Will extra
rainfall be cancelled out by extra evaporation? Will the fertilising
effect of carbon dioxide be more powerful than the heat damage it
causes? To what extent will farmers be able to adapt? Will new varieties
of crops keep up with the changing weather?
But, to put it very
broadly, the consensus is that climate change will hurt farmers in the
tropics and help farmers in temperate countries. A famous paper published in 2005
concluded that if we follow the most extreme trajectory for greenhouse
gas production (the one we happen to be on at the moment), global
warming would raise harvests in the rich nations by 3% by the 2080s, and
reduce them in the poor nations by 7%. This gives an overall reduction
in the world's food supply (by comparison to what would have happened
without manmade climate change) of 5%.
Papers published since then
support this conclusion: they foresee hard times for farmers in Africa
and south Asia, but a bonanza for farmers in the colder parts of the
world, whose yields will rise just as developing countries become less
able to feed themselves. Climate change is likely to be devastating for
many of the world's poor. If farmers in developing countries can't
compete, both their income and their food security will decline, and the
number of permanently malnourished people could rise. The nations in
which they live, much of whose growth was supposed to have come from
food production, will have to import more of their food from abroad. But
in terms of gross commodity flows the models do not predict an
insuperable problem.
So here's where the issue arises. The models
used by most of these papers forecast the effects of changes in averaged
conditions. They take no account of extreme weather events.
Fair enough: they're complicated enough already. But what if changes in
the size of the global harvest are determined less by average conditions
than by the extremes?
This is what happened in 2012. This is what
seems likely to happen in subsequent years. Here's why. A paper this
year by the world's leading climate scientist, James Hansen, shows that
the frequency of extremely hot events (such as the droughts which
hammered the US and Russia) has risen by a factor of about 50 by comparison with the decades before 1980.
Forty years ago, extreme summer heat typically affected between 0.1 and
0.2% of the globe. Today it scorches some 10%. "We can project with a
high degree of confidence," the paper warns, "that the area covered by
extremely hot anomalies will continue to increase during the next few
decades and even greater extremes will occur." Yet these extremes do not
feature in the standard models predicting changes in crop production.
If
the mechanism proposed by another paper is correct, it is not just
extremes of heat that are likely to rise. I've explained this before,
but I think it's worth repeating. The jet stream is a current of air
travelling eastwards around the upper northern hemisphere. It separates
the cold wet weather to the north from the warmer, drier weather to the
south. Wobbling along this ribbon are huge meanders called Rossby waves.
As the Arctic heats up, the meanders slow down and become steeper. The
weather gets stuck.
Stuck weather is another way of saying extreme
weather. If the jet stream is jammed to the north of where you are, the
weather stays hot and dry, and the temperature builds up – and up. If
it's lodged to the south of you, the rain keeps falling, the ground
becomes saturated and the rivers burst their banks. This summer the UK
and the US seem to have found themselves on opposite sides of stuck
meanders, and harvests in both countries were savaged by opposing
extremes of weather.
This is where we stand with just 0.8 degrees
of global warming and a 30% loss of summer sea ice. Picture a world with
two, four or six degrees of warming and a pole without ice, and you get
some idea of what could be coming.
Farmers in the rich nations
can adapt to a change in averaged conditions. It is hard to see how they
can adapt to extreme events, especially if those events are different
every year. Last winter, for example, I spent days drought-proofing my
apple trees, as the previous spring had been so dry that – a few weeks
after pollination – most of the fruit shrivelled up and died. This
spring was so wet that the pollinators scarcely emerged at all: it was
the unfertilised blossom that withered and died. I thanked my stars that
I don't make my living this way.
Perhaps there is no normal any
more. Perhaps the smooth average warming trends that the climate models
predict – simultaneously terrifying and oddly reassuring – mask wild
extremes for which no farmer can plan and to which no farmer can
respond. Where does that leave a world which must either keep raising
production or starve?
note: I fear our time is VERY quickly running out; it's time to prepare and stock up NOW!
