Page 338 - Climate Change and Food Systems

climate change and food systems: global assessments and implications for food security and trade
century is very likely (more than a 90% chance) due to observed increase in anthropogenic greenhouse gas concentrations”, Intergovernmental Panel on Climate Change (IPCC, 2007, WG1).
■ “There is strong evidence that the warming of the Earth over the last half-century has been caused largely by human activity, such as the burning of fossil fuels and changes in land use”, The Royal Society (2010).
■ “A strong, credible body of scientific evidence shows that climate change is occurring, is caused largely by human activities, and poses significant risks for a broad range of human and natural systems”, United States National Science Academy (2010).
A recent study by Huber and Knutti (2012) reported that at least three-quarters of the temperature rise observed in the past 60 years
is due to human activity and that natural climate variability is extremely unlikely to have contributed more than one-quarter of the observed global warming. The study findings reinforce previous reports that greenhouse gases, in particular CO2, are the main cause of recent global warming. It calculated a net warming value of 0.5oC (since the 1950s), which is very close to the actual observed temperature rise of 0.55oC. The study was also
able to model the contribution of solar radiation, commonly cited by climate sceptics as the cause of global warming. Solar radiation only contributed around 0.07oC of the recent warming. This study produces even higher confidence that human- induced causes dominate the observed global warming.
Finally, the IPCC 5th Assessment Report, published recently, concluded that “there is a clear human influence on the climate” and that “it is extremely likely that human influence has been the dominant cause of observed warming since 1950” (IPCC, 2013a).
3. Climate variability and agriculture
Agriculture is sensitive to variability in weather and climate (principally rainfall and temperature) at a range of time and spatial scales, as evidenced from observations of crop plants, the behaviour of soft commodity prices and the productivity of the entire agricultural sector.
In many monsoon-affected regions of the world, clear, large-scale correlations are seen between seasonal rainfall and national crop yields and even gross national products (GNPs). For example, between 1966 and 1990, the total
figure 2
Decadal land-surface average temperature (from Richard, 2012; Figure at
http://www.bbc.co.uk/news/science-environment-15373071
Temperature anomaly (oC)
1.0 0.5 0 -0.5 -1.0 -1.5
1800 1820 1840
Source: Berkeley Earth Project
1860 1880 1900
1920 1940
1960 1980 2000
Statistical/spatial uncertainty interval Berkeley
NASA GISS NOAA HadCRU
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