The next month or two will go a long way to determining whether 2010 is to be the hottest year since temperature record began in the mid-1800s.

Whether this occurs or not has implications for the climate change debate because a key argument among climate change sceptics in recent years is that global warming “stopped in 1998”, based on the fact that the average annual temperature following that peak year has not been surpassed.

The US National Oceanic and Atmospheric Administration (NOAA) has confirmed that last month was the hottest June ever recorded, following a monthly pattern set in the previous four. The period from January to June period saw the warmest combined global land and ocean surface temperatures since 1880, the NOAA said.

That puts 2010 on course to eclipse 1998 as the hottest year on record and scientists will probably have a good idea after the end of the Northern Summer in September. This is also the month that the seasonal Arctic ice-melt peaks, another key measure of global warming. By July 1 this year, ice retreat had already surpassed that of any previous year putting 2010 on a course to exceed the record retreat of 2007.

The cyclical El Nino weather pattern which warms the Pacific Ocean is major factor contributing to the record years – 1998 and 2010 corresponding with such events.
Climate scientists say that distilling evidence of long-term global warming from seasonal and cyclical variability is very difficult and can’t be done by comparing individual years, only trends across decades or more.

To this end, the latest NOAA data shows June was the 304th consecutive month with a global surface temperature above the average over the last century. That’s a period of 25 years. This decade, 2000-2010, is also the warmest decade on record, and the ten warmest years recorded since 1900 have all occurred in the last 15 years.

AFP 20/07/10