Earth 'at warmest for 11,300 years'
Published 07/03/2013 | 19:46
Earth is warmer today than it has been for most of the last 11,300 years, new research has shown.
Scientists studied fossils recovered from 73 sites around the world to track global climate to the end of the last Ice Age.
They found that for 70% to 80% of this period, which dates back to the start of the holocene era in which we now live, temperatures were cooler than they are now.
Lead researcher Dr Shaun Marcott, from Oregon State University in the United States, said: "We already knew that on a global scale, Earth is warmer today than it was over much of the past 2,000 years. Now we know that it is warmer than most of the past 11,300 years. This is of particular interest because the holocene spans the entire period of human civilisation."
The study, published in the journal Science, provides the first truly global view of climate at millennia timescales. Many previous temperature reconstructions have been based on regional data, according to co-author Professor Peter Clark, also from Oregon State University.
"When you just look at one part of the world, the temperature history can be affected by regional climate processes like El Nino or monsoon variations," said Prof Clark. "But when you combine the data from sites all around the world, you can average out those regional anomalies and get a clear sense of the Earth's global temperature history."
The research shows that over the past 5,000 years the Earth underwent an overall cooling of around 0.5C. But in just the last 100 years - since the start of the industrial age - it has warmed by the same amount. The biggest changes were in the northern hemisphere, where there is a greater density of human population.
Climate models predict that by 2100 the global temperature could rise by another 1C to 6C depending on the level of greenhouse gas emissions. "What is most troubling is that this warming will be significantly greater than at any time during the past 1,300 years," said Prof Clark.
The scientists point out that, because of its position relative to the Sun, the Earth should now be near the bottom of a long-term cooling trend. Yet this is clearly not the case.
Candace Major, from the US National Science Foundation's Division of Ocean Sciences, which funded the research, said: "This research shows that we've experienced almost the same range of temperature change since the beginning of the industrial revolution as over the previous 11,000 years of Earth history - but this change happened a lot more quickly."