Development Roast Giving international development a proper roasting
By: Lykke E. Andersen*
There is little doubt that human greenhouse gas emissions, mainly arising from the burning of fossil fuels and forests, are warming the planet. The physical properties of CO2 in the atmosphere imply that a doubling of CO2 concentrations from the current 400 parts per million (ppm) to 800 ppm would directly cause an increase in the average global temperature of about 1°C, and with that increase in temperatures we would also experience an increase in global precipitation. That much we know with a high degree of certainty.
Anything beyond that, however, is highly uncertain. While most climate models incorporate positive feedback effects that amplify the initial direct warming effect several times, historical data suggests that there are important negative feedbacks that help stabilize global temperatures. Most importantly, Earth’s temperature has oscillated within a relatively narrow band for hundreds of millions of years despite much higher and much lower CO2 concentrations in the past (see Figures 1 and 2). In addition, during the last couple of decades, global temperatures have not increased nearly as much as suggested by the models with strong positive feedbacks. Thus, we should have only low confidence in our knowledge about feedback effects and temperature increases beyond 1°C.