The Earth鈥檚 rapid warming has pushed temperatures to their hottest level in nearly 12,000 years 鈥� and a hair鈥檚 breadth away from a million-year peak 鈥� according to a NASA study.
Global warming, which has increased temperatures by 0.2掳C per decade over the past 30 years, has caused temperatures to reach and now pass through the warmest levels in the current interglacial period, which lasted almost 12,000 years.
The study, led by James Hansen and colleagues at NASA鈥檚 Goddard Institute for Space Studies, reports that Earth is now within about 1掳C of the maximum estimated temperature of the past million years.
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鈥淭hat means that further global warming of 1.0掳C defines a critical level. If warming is kept less than that, effects of global warming may be relatively manageable,鈥� he says.
Different planet
鈥淒uring the warmest interglacial periods the Earth was reasonably similar to today. But if further global warming reaches 2掳C or 3掳C, we will likely see changes that make Earth a different planet than the one we know.鈥�
Hansen points out that the last time temperatures on Earth were that warm was in the middle Pliocene, about three million years ago, when sea levels were estimated to have been about 25 metres higher than today.
The repercussions of current warming are already being felt, researchers point out. 鈥淰egetation cover is already expanding towards the pole in the Northern Hemisphere,鈥� causing yet further warming, Hansen says. He adds that such global warming could result in the release of further large amounts of greenhouse gas emissions. 鈥淪ome of the largest warmings in the Earth鈥檚 history, and mass extinctions, may be associated with such release.鈥�
The researchers say that curbing carbon dioxide emissions will be vital in reducing the escalation in warming, but other methods should also be attempted. They suggest, for example, that ships could be deployed in ocean regions to seed clouds, which would help reflect the Sun鈥檚 heat and provide some much needed shade.
Journal reference: Proceedings of the National Academies of Sciences (DOI: 10.1073/pnas.0606291103)
