Is Our Climate Changing?

This July has been the hottest on record for the lower 48 states since record keeping began in 1895. For New Yorkers, that has meant more extreme
rain and thunderstorms. For the nation’s breadbasket, this summer is hotter than the Dust Bowl days of the mid 1930s.

Climate scientists are starting to draw some cause and effect relationships between the continued climb of emissions into the atmosphere and the cascade of extreme weather we are experiencing.

In a new paper, Public Perception of Climate Change and the New Climate Dice, Jim Hansen and two colleagues explore the following question: “Should the public be able to recognize that climate is changing, despite the notorious variability of weather and climate from day to day and year to year?”

As Hansen puts it, "Climate dice", describing the chance of unusually warm or cool seasons relative to climatology, have become progressively "loaded" in the past 30 years, coincident with rapid global warming.

Hansen and his colleagues conclude:  “Thus we can state with a high degree of confidence that extreme summers, such as those in Texas and Oklahoma in 2011 and Moscow in 2010, are a consequence of global warming, because global warming has dramatically increased their likelihood of occurrence.”

Their maps of the 20th century history of global surface temperatures are viewable here.

One paragraph stands out in particular for its jargon-free clarity:

“Summer, when most biological productivity occurs, is the most important season for humanity and thus the season when climate change may have its biggest impact. Global warming causes spring warmth to come earlier and it causes cooler conditions that initiate
fall to be delayed. Thus global warming not only increases summer warmth, it also protracts summer-like conditions, stealing from both spring and fall. Our study therefore places emphasis on study of how summer temperature anomalies have been changing.”

The World Wildlife Fund’s Lou Leonard offers a thoughtful reflection on 1988 v. 2012. In 1988, the US faced an extreme drought, second only to 2005 Katrina in expense to the US economy as a “natural” disaster. That too, was election year. This year’s drought is now parching over 60% of the lower 48 states, and will exceed 1988 in impact.  

Are Americans are starting to connect the climate dots between the emissions we put in the atmosphere and the weather extremes?  Yes.

A recent University of Texas poll showed that 70% of respondents agree that climate is changing--up from 65 percent in March. Whether that perception turns into more climate friendly policy and behavior remains to be seen.