The Climate And Energy State Of The Union
How about a “balanced approach” to energy and climate policy?
In his State of the Union speech, President Barack Obama warned that Americans must take steps now to cut “our emissions of the dangerous carbon pollution that threatens our planet.” To justify these efforts, he appealed to the “overwhelming judgment of science,” pointing chiefly to recent weather extremes in the United States as evidence for the urgency of action. Skeptics “can choose to believe that Superstorm Sandy, and the most severe drought in decades, and the worst wildfires some states have ever seen were all just a freak coincidence,” Obama announced, but the president clearly does not. “Heat waves, droughts, wildfires, floods—all are now more frequent and more intense.”
Is he right? Let’s take a closer look at those trends the president cites. After that, we can assess the he wants to implement as a response.
Heat, Drought, Fires, and Floods
Let’s start, as Obama did, with heat waves. According to the National Oceanic and Atmospheric Administration, last year was the hottest year since 1895 for the contiguous United States, about 3.2 degrees Fahrenheit above the 20th century average. Globally, 2012 was the tenth warmest year on record, and all 12 years to date in the 21st century rank among the 14 warmest since 1880. On the other hand, the Environmental Protection Agency’s Heat Wave Index from 1895 to 2011 shows that the frequency and breadth of heat waves in the lower 48 states were dramatically more severe in the 1930s than at any other time in the historical record, although there has been an uptick in recent years. A study in the January 2013 issue ofClimatic Change, analyzing trends in monthly mean temperatures around the globe since the 1880s, reports that “the number of record-breaking heat extremes has on average increased to roughly 5 times the number expected in a climate with no long-term warming.”
With regard to droughts, the Palmer Drought Severity Index for the continental U.S. reveals that the 1930s and 1950s saw the most widespread droughts since the record begins in 1895; the last 50 years have generally been wetter than average. In 1934about 80 percent of the lower 48 experienced drought. The next worst years were 1954 and 2012, when more than 60 percent of the contiguous U.S. suffered drought. The most recent data show that the drought in the middle section of the country has not yet abated. Interestingly, even as average global temperatures have increased, a study published inNature in November 2012 argued that the index overestimated the increase in global drought and that “there has been little change in drought over the past 60 years.”
Last year was America’s third biggest year for wildfires since 1960, with just 2006 and 2007 coming out ahead. Each of those years saw more than 9 million acres burn, according to data from the National Interagency Fire Center (NIFC). Between 1960 and 2000, an average of about 3.7 million acres of wildlands burned every year. Since 2000, the average has been about 7 million acres. In the 1930s, by contrast, about 40 to 50 million acres of wildlands burned annually, dropping below 10 million acres by the mid-1950s. (It’s hard to get good data on the trends prior to the ’30s.) The 52-year average of the NIFC data is 4.5 million acres per year, so the area burned by wildfires each year has declined by more 90 percent since the 1930s. Still, the current trajectory doesn’t look good: In December NASA researchers reported that climate models project that “high fire years like 2012 would likely occur two to four times per decade by mid-century, instead of once per decade under current climate conditions.”
What about flooding? A 2011 study by the U.S. Geological Survey looked at data from stream gauges collected over the past 127 years in four regions of the U.S. The hydrologists found no “strong statistical evidence for flood magnitudes increasing” with carbon dioxide. The EPA does report that precipitation in the lower 48 is increasing at a rate of 5.9 percent per century. The EPA also notes, drawing on data from 1910 and 2011, that extreme precipitation events(defined as being in the top 10 percent of one-day events) over the conterminous U.S. states are also increasing. Other studies find that the frequency of extreme precipitation events is also increasing globally.
As noted above, Obama also invoked Superstorm Sandy as evidence of dangerous man-made climatic trends. Sandy was especially disastrous because it combined with a snowstorm and came ashore when the local tides were running high. But is Sandy evidence of worsening global hurricane trends? It’s worth recalling the reason that Sandy was dubbed a “superstorm”: It was no longer a hurricane when it hit the northeastern United States. In his 2011 article for Geophysical Research Letters, “Recent Historically Low Global Tropical Cyclone Activity,” the atmospheric scientist Ryan Maue reports that accumulated cyclone energy (ACE) has recently been at a 40-year low.
ACE measures each tropical storm’s wind energy. Even though Sandy was a monster storm, the North Atlantic ACE measure for 2012 was the 20th highest out of the last 62 years. Less happily, climate computer models project that future warming will likely cause hurricanes globally to increase in average intensity by between 2 to 11 percent.
On balance, then, currently available scientific evidence indicates that heat waves and wildfires in the U.S. have increased in recent years. On the other hand, there appear to be no strong trends for droughts, floods, and hurricanes in the continental United States. However, most climate computer models suggest that all of these aspects of climate will get worse as the century unfolds.