When it comes to climate change and its impacts on agriculture, we may know less than we think.
But according to David Lobell, Assistant Professor in Stanford’s Department of Environmental Earth System Science, acknowledging the gaps in our understanding could help us to more effectively prepare the world’s food system for a warmer future.
Lobell, who has built an impressive career around the study of climate change and its implications for global food security, addressed the topic of agricultural adaptation during a two-hour symposium held on the Stanford campus in early December. His presentation summarized the strengths and weaknesses of climate models in the context of global agriculture, and suggested broad strategies for preparing agriculture for climate change’s inevitable impacts.
Lobell began his talk by reaffirming some common beliefs. The Earth as a whole is unquestionably warming, he said. Precipitation intensity is increasing in high-rainfall areas, and the world’s driest regions are becoming drier.
“Think about the hottest day we currently experience in a 20-year period,” Lobell told listeners. “By mid-century, we’ll be seeing that hottest day every year, as opposed to every 20 years.” During the same period, soil moisture content in many of the world’s major agricultural areas will decrease by as much as 10 to 15 percent, while annual precipitation at the equator and high latitudes will increase by several inches per year.
At the global scale, Lobell said, climate change will have a net negative impact on existing agricultural systems. The world’s rainfed farms will become increasingly vulnerable to heat and water stress. Growing ranges and seasons for heat-intolerant crops, such as wheat and sorghum, will contract. Although the high latitudes may see some gains from warmer temperatures and CO2 fertilization of certain crops, low-latitude regions – including South Asia and much of Africa – will suffer disproportionate yield losses as temperatures rise.
However, Lobell said that impacts aimed at local and national scales, as opposed to broad regions or the world as a whole, are much more difficult to predict. A moderate change in average rainfall across a continent could translate to drastic increases or decreases in individual countries. For example, while climate models suggest that Africa’s annual rainfall will change by less than 10 percent over the next 50 years, model projections show rainfall in the nation of Sengal changing by anywhere from five to 40 percent over the same period.
Additionally, Lobell said, forecasts of increasing climate variability are frequently overstated. “The number one misperception I hear is that climate change is going to mean more variability,” he noted. In fact, model projections of year-to-year variability in temperature and precipitation cover a wide range. Some models do show large increases in variability over the next century – but others show a slight decrease.
Because we understand climate impacts best at the long-term and global scales, Lobell said, global responses that address long-term trends are the most likely to serve our future needs. He cautioned against approaches that prepare farmers for short-term variability, such as sudden floods or droughts, but fail to acknowledging the effects of steadily rising average temperatures. He also stressed the value of globally coordinated efforts, particularly those aimed at developing better heat and drought-tolerant crop varieties, to supplement local infrastructure projects.
“We’re in a world where local resilience depends on global systems,” Lobell noted. He said that the interconnectedness of modern global food markets makes global trends, and global responses, increasingly relevant for local food security.
At both local and global levels, an effective response to climate change will require robust social institutions. Dr. Fatima Denton, Program Leader for Climate Change Adaptation in Africa for the Consultative Group on International Agricultural research, stressed this point in her comments on Lobell’s presentation. “Climate change has really unmasked our governance challenges and the weaknesses in our institutions,” Denton said. “This is not just about biophysical processes…it’s about the development pathways that we choose.”
Lobell agreed. Climate change, he said, presents “an important opportunity for transformation.” He encouraged present and future leaders to think critically about all aspects of the relevant science and policy. “Be skeptical of what you hear,” he advised, “and educate yourself about what we do and don’t know.”
This was the sixth talk in FSE's Global Food Policy and Food Security Symposium Series.
FSI scholars approach their research on the environment from regulatory, economic and societal angles. The Center on Food Security and the Environment weighs the connection between climate change and agriculture; the impact of biofuel expansion on land and food supply; how to increase crop yields without expanding agricultural lands; and the trends in aquaculture. FSE’s research spans the globe – from the potential of smallholder irrigation to reduce hunger and improve development in sub-Saharan Africa to the devastation of drought on Iowa farms. 
