The global temperature numbers have been crunched for the month of July and depending on who crunched the data, July was somewhere between the third and sixth warmest on record. Land-based observations had July as the fifth warmest on record, while ocean-based observations had that region as the 11th-warmest July on record. Combining the two gives the planet as a whole the rating of the third-warmest July on record.
If you’re skeptical about surface-based observations being an accurate way of comparing temperature trends, let’s look at what the satellite-based temperature records of the lowest eight kilometres of the atmosphere showed. According to these records, which go back 34 years, July was either the third warmest or the sixth warmest, according to the two different organizations that calculate this number.
If we look at this issue’s map that shows the temperature anomalies across the globe during July, we can see that much of central and eastern North America saw well-above-average temperatures during the month, with slightly belowaverage temperatures over the far-western parts of North America. The only place on the planet that was well below average for July was the area over central Russia.
So far during 2011 there have been six all-time-high national temperature records set, and in 2010 we saw 20 all-time national heat records broken. Also during this time period, Asia recorded six of the hottest temperatures ever, with temperatures peaking at 53.5 C at Moenjodaro, Pakistan on May 26, 2010. The all-time record for the planet is 54 C, measured at Tirat Zvi, Israel on June 21, 1942, but this record appears to be in error, as a misread of the thermograph indicated 54 C but it actually read only 53 C. This record of 53.5 C comes close to breaking what is now considered the most reliable all-time temperature record for the planet of 53.9 C, that has occurred three times at the appropriately named Furnace Creek in Death Valley, Calif. between 1998 and 2007.
It is interesting that while the planet has seen several alltime national-high temperature records broken over the last couple of years, there have been no national all-time-low temperature records broken.
Sea ice decline continues
Looking to our north during July we see that the amount of Arctic sea ice has hit an alltime record low. According to the National Snow and Ice Data Centre, the average ice extent for July 2011 was 7.92 million square kilometres (3.06 million square miles). This was 210,000 square km (81,000 square miles) below the previous record low for the month, which was set in July 2007, and 2.18 million square km (842,000 square miles) below the average for 1979 to 2000. The amount of ice loss slowed during the last part of July and the beginning of August, but it has now increased again. Both the Northwest and Northeast passages are now relatively ice free. This is only the third time in history that they have been open and all three times have occurred in the last three years. Total ice volume in the Arctic also continued to decline, as the amount of thick multi-year ice slowly disappears. It is looking very likely that the total volume of Arctic sea ice will hit an alltime low later this summer.
Finally, if we look west over the Pacific Ocean we see that ocean temperatures are in what is considered a neutral temperature range, neither El Nińo or La Nińa. The computer models are divided as to what might happen as winter approaches, with about an equal number showing weak El Nińo conditions to develop, remaining neutral, or weak La Nińa conditions developing. Chances are, we will continue to see natural conditions persist, which means it will be tough to figure out what kind of winter might be in store for us this year – but more about that in a couple of months.