The Earth is entering a period of climate change faster than in the last 1,000 years, suggests an analysis of the planet's climate that focused on decades instead of centuries.
Temperatures fluctuated by 0.2 deg c in the last 1,000 years but went up to 0.4 deg per decade in the last 40 years.
By 2020 the warming will be much more than in the last 2,000 years and rise further if current trends continue.
Europe, North America and the Arctic will feel the transition first. In the Arctic the temperature can see a 1.1 deg rise by 2040.
The study examined historical and projected changes over decades to determine the temperature trends that will be felt by humans alive today.
Steve Smith and colleagues at the Department of Energy's Pacific Northwest National Laboratory published a paper based on their study in Nature Climate Change.
"We focused on changes over 40-year periods, which is similar to the lifetime of houses and human-built infrastructure such as buildings and roads," said lead author Smith. "In the near term, we're going to have to adapt to these changes."
To examine rates of change, the team turned to the Coupled Model Intercomparison Project which combines simulations from over two dozen climate models from around the world.
The team calculated how fast temperatures changed between 1850 and 1930, a period when the amount of fossil fuel gases in the atmosphere was low. They compared these rates to temperatures reconstructed from tree ring records, corals and ice cores, for the past 2,000 years.
The shorter time period simulations were similar to the reconstructions over a longer time period, indicating robustness of the model used.
While there was little average global temperature increase in the early time period, the Earth's temperature fluctuated in the past due to natural variability.
Rise in North America and Europe
But rates of change over the earlier 40-year periods in North America and Europe rose and fell as much as 0.2 degrees Celsius per decade.
In the period between 1971 and 2020 this went up with the average rate of change over North America touching about 0.3 degrees Celsius per decade, beyond natural variability.
At the present time, most world regions are almost completely outside the natural range for rates of change.
Calculating for the coming 40 years, climate change picked up speed in all cases, even in scenarios with lower rates of future greenhouse gas emissions.
At high greenhouse gas emissions, increased rates of change were seen throughout the rest of the century.