January-July 2010 warmest on record — just as a low in solar energy should have been cooling the Earth
UPDATE: Yesterday GISS released the data on which this post was originally based. Today, they released a full analysis under this headline: “July 2010 — What Global Warming Looks Like.”
The analysis notes that La Niña conditions currently developing in the Pacific should act to tamp down global temperatures during the remainder of the year. Even so, the GISS researchers say the warming of the first seven months of the year has been so pronounced that “2010 is likely, but not certain, to be the warmest year in the GISS record.”
Based on the analysis released today, I’ve made a couple of changes to my post from yesterday. Most significantly, I corrected a factual error. Yesterday I stated that this past July was the fifth warmest on record. I misread the data. It was actually close to being the third warmest in the GISS record.
NASA’s Goddard Institute for Space Studies has just released its monthly analysis of global temperatures, and the news is that January through July comprised the warmest such period in 131 years of record keeping.
For that seven month period, the mean surface temperature of the Earth (including both the land and ocean surfaces) was 0.69 degrees C warmer than the 1951-1980 average, according to the calculations by GISS scientists.
The global temperature for July itself was 0.55 degrees C warmer than the long term average, “which puts 2010 in practically a three way tie for third warmest July,” according to GISS.
The global average temperature of one month, or even seven months, does not a trend make. But this year’s continuing spate of hot weather serves as a kind of exclamation point on a clear long-term trend of rising global temperatures.
As the following anomaly maps from GISS show, each of the decades since the 1970s has been warmer than the one before it, with 2000 to 2010 being hotter than all the others.
“Global warming on decadal time scales is continuing without letup,” conclude James Hansen and colleagues at GISS, writing in a paper that has been accepted for publication in Reviews of Geophysics.
As the second of the following graphs shows, the 12-month running mean of global average temperature also set a new record in 2010, reaching more than 0.6 degrees C above the 1951 to 1980 base period. That’s a warmer anomaly in the 12-month running mean than has ever been seen before.
The records set so far in 2010 are particularly noteworthy, according to Hansen, because they came at the end of a period during which the Earth was receiving a relatively low amount of solar energy.
The graph below shows “solar irradiance,” a measure of how much solar energy the Earth received from 1975 through the recent solar minimum. As the graph reveals, solar activity is cyclical. Look to the extreme right of the graph and you’ll see that the Sun is now pulling out of a more quiescent phase. The minimum of the most recent cycle is marked “Min23/24.”
The continuing trend toward higher temperatures at a time when solar energy has been ebbing simply highlights something that climate scientists have known for decades: humans are heating the climate system through emissions of carbon dioxide and other greenhouse gases.
NOTE: I have emailed James Hansen to ask for comments on the new analysis. I’ll post updates when I hear back from him.