The Earth’s fast-warming climate may be teetering on irreversible, catastrophic shifts in temperatures, rainfall, ice shrink and permafrost melt — leaving only a few years for people to slash human-generated greenhouse gas emissions.
Such was the warning emerging from various panels at the annual meeting of the American Geophysical Union this past week in San Francisco, including a session that focused solely on “tipping points” of climate change.
Rising sea levels, warming permafrost, startling melt rates in Greenland, droughts, coral bleaching, heat waves, changes in snowfall and precipitation all contribute to the alarm. But exhibit A remains the stupendous and unprecedented meltback of the Arctic Ocean’s ice extent during the summer of 2007.
“An already relentless melting of the Arctic greatly accelerated this summer, a warning sign that some scientists worry could mean global warming has passed an ominous tipping point,” wrote AP’s Seth Borenstein, in a story that ran last week.
“One even speculated that summer sea ice would be gone in five years. Greenland’s ice sheet melted nearly 19 billion tons more than the previous high mark, and the volume of Arctic sea ice at summer’s end was half what it was just four years earlier.
“At this rate, the Arctic Ocean could be nearly ice-free at the end of summer by 2012, much faster than previous predictions,” NASA climate scientist Jay Zwally told Borenstein.
“The Arctic,” said Mark Serreze, senior scientist at the National Snow and Ice Data Center and one of AGU’s invited lecturers this year, ” is screaming.”