Guest essay by Eric Worrall

Another global warming food security study based on unrealistic assumptions.

The global corn crop is vulnerable to the effects of climate change

By ADAM WERNICK

Corn, also known as maize, is the world’s most-produced food crop. But it could be headed for trouble as the Earth warms.

A new study published in Proceedings of the National Academy of Sciences of the United States of America finds that climate change will not only increase the risk of food shocks from world corn production but that these crop failures could occur simultaneously.

“Increased warming leads to global crop failures because plants are not adapted to really high temperatures,” explains Michelle Tigchelaar, a research associate at the University of Washington. “Most of our crops are really well-adapted for our current climate. There is an optimum temperature at which they grow and beyond that their yields decline. Extreme heat has really negative impacts on … the flowering of crops and also increases their water usage.”

…

“So, it really does matter if we have two or four degrees of warming,” Tigchelaar says. “It’s not just ‘any warming is bad’ or “any warming doesn’t matter.” It really matters where on that spectrum we land.”

…

Farmers may be able to find ways to adapt to new conditions. For example, Tigchelaar says her study did not look at the extent to which growing regions could shift. “Already we see that wheat is expanding northward,” she explains. “So, we might be able to soon grow corn in places we couldn’t grow it before. Similarly, farmers might decide to shift their planting dates to avoid the hottest time of the year.”

…

Read more: http://news.wbfo.org/post/global-corn-crop-vulnerable-effects-climate-change

The abstract of the study;

Future warming increases probability of globally synchronized maize production shocks

Michelle Tigchelaar, David S. Battisti, Rosamond L. Naylor, and Deepak K. Ray

Meeting the global food demand of roughly 10 billion people by the middle of the 21st century will become increasingly challenging as the Earth’s climate continues to warm. Earlier studies suggest that once the optimum growing temperature is exceeded, mean crop yields decline and the variability of yield increases even if interannual climate variability remains unchanged. Here, we use global datasets of maize production and climate variability combined with future temperature projections to quantify how yield variability will change in the world’s major maize-producing and -exporting countries under 2 °C and 4 °C of global warming. We find that as the global mean temperature increases, absent changes in temperature variability or breeding gains in heat tolerance, the coefficient of variation (CV) of maize yields increases almost everywhere to values much larger than present-day values. This higher CV is due both to an increase in the SD of yields and a decrease in mean yields. For the top four maize-exporting countries, which account for 87% of global maize exports, the probability that they have simultaneous production losses greater than 10% in any given year is presently virtually zero, but it increases to 7% under 2 °C warming and 86% under 4 °C warming. Our results portend rising instability in global grain trade and international grain prices, affecting especially the ∼800 million people living in extreme poverty who are most vulnerable to food price spikes. They also underscore the urgency of investments in breeding for heat tolerance.

Read more: http://www.pnas.org/content/115/26/6644/

Whenever I see a study like this, I just think – why?

Michelle Tigchelaar to her credit admitted that farmers might be able to adapt to changed conditions, that they are already adapting to changed conditions.

So why try to make the study seem frightening, why claim the world faces the risk of famine, instead of just saying that growing regions might shift a little if the planet warms?

Even if 4C warming actually occurs, a 200 mile shift in growing regions would fix the problem. Even if we ignore what eighty years of advances in genetic engineering will do for crop resilience, there are vast regions adjacent to existing corn belts which are currently too cold, regions which could be brought into production in a warmer world.

There is no chance a 4C warming would cause a net loss of global corn production.

Besides, there’s this; in the last few “hottest years ever” global corn production continues to rise.

From the article:

Since 1990, 56% of the increase in world corn production has been achieved through higher yields, and the remaining 44% has come from increased acres in corn production.