Climate Change Index for week ending 20 Sept. 2009

Today we introduce a new weekly feature — the Climate Change Index — that tracks research findings and events directly attributable to global warming. Our aim is to provide a numerical, week-to-week indicator of climate change developments.

Items that qualify for listing in each week’s index include new climate data published in peer-reviewed academic journals and extreme weather incidents or other natural events that are likely directly linked to the global warming trend.

The Climate Change Index for this week, ending 20 Sept. 2009 (details below): 4

18 September: US Geological Survey researchers spot the carcasses of between 100 and 200 walruses along the northwest coast of Alaska. While the cause of death has yet to be determined, scientists are seeing walruses gathering in unusually large numbers on shore, as opposed to on sea ice. They attribute the shift to the fact that sea ice has now moved beyond the continental shelf over waters too deep for walruses to feed in.

17 September: Arctic sea ice cover reaches its seasonal minimum — the third-lowest extent ever recorded (after record lows in 2007 and 2008). This year’s minimum, occurring on 12 September, was 5.10 million square kilometres, compared to 4.52 million square kilometres in 2008 and 4.13 million square kilometres in 2007. The National Snow and Ice Data Centre adds, “While the ice extent this year is higher than the last two years, scientists do not consider this to be a recovery. Despite conditions less favorable to ice loss, the 2009 minimum extent is still 24% below the 1979-2000 average, and 20% below the thirty-year 1979-2008 average minimum. In addition, the Arctic is still dominated by younger, thinner ice, which is more vulnerable to seasonal melt. The long-term decline in summer extent is expected to continue in future years.”

16 September: The US National Climatic Data Centre, part of the National Oceanographic and Atmospheric Administration, report that the world’s ocean surface temperature was the warmest for any August on record, and the warmest on record averaged for any June-August (Northern Hemisphere summer/Southern Hemisphere winter) season.

14 September: Research from the University of California – Berkeley finds that 48 of 53 bird species studied in California’s Sierra Nevada mountains have adjusted to climate change over the last century by moving to sites with the temperature and precipitation conditions they favored.