Loading...
HOME
POLITICS
CLIMATE
BUSINESS
SCIENCE
WORLD
HISTORY
LIFESTYLE
EDITORIAL
RESOURCES
CONTACT

FEATURE

Perceptions of Climate Change





AnswerTips-Enabled

by James Hansen and Makiko Sato

This past winter, for the second year in a row, seemed pretty extreme in both Europe and the United States. So this is a good time to check quantitatively how seasonal climate change is stacking up against expectations.

People's perception of climate change may be the most important factor determining their willingness to accept the scientific conclusion that humans are causing global warming (or global climate disruption, as you please). It is hard to persuade people that they have lying eyes.

In the paper attached to my congressional testimony in 1988 (1) we asserted that the perceptive person would notice that climate was changing by the early 21st century. I used colored dice to illustrate how the frequency of unusually warm seasons was expected to change.

We considered three scenarios for future greenhouse gas amounts. Figure 1 shows that the real world so far is close to scenario B. Temporary aside: there are two main reasons that greenhouse gas growth moved off the track of scenario A onto scenario B in the early 1990s, as shown in Figure 2: (1) the growth of CFCs (chlorofluorocarbons) was greatly diminished by successive tightenings of the Montreal Protocol, (2) the growth of methane slowed sharply.



Fig. 1. Update of Fig. 2 of Reference 1, scenarios A, B and C being climate forcings of greenhouse gases used in climate model simulations. The real world (red curve) has closely followed scenario B.





Fig. 3. Surface temperature anomalies in Northern Hemisphere winter 2010-2011 relative to 1951-1980 mean. See reference 3.

Let's start with this past winter, compare it with the last few winters, and then check whether the odds of warm seasons have changed as expected.   Continued...


[ [1] 2 ] read more →

IN THIS ISSUE