Natural climate change may be larger than commonly thought

February 10, 2005

A new study of climate in the Northern Hemisphere for the past 2000 years shows that natural climate change may be larger than generally thought. This is displayed in results from scientists at the Stockholm University, made in cooperation with Russian scientists, which are published in Nature on 10 Feb 2005.

The most widespread picture of climate variability in the last millennium suggests that only small changes occurred before the year 1900, and then a pronounced warming set in. The new results rather show an appreciable temperature swing between the 12th and 20th centuries, with a notable cold period around AD 1600. A large part of the 20th century had approximately the same temperature as the 11th and 12th centuries. Only the last 15 years appear to be warmer than any previous period of similar length.

This study builds on an analysis of indirect climate data, such as information from ocean and lake bottoms, ice sheets, caves and annual tree rings. The use of this kind of material to reconstruct climate far back in the past is nothing new in itself. The difference between the new study from previous ones, is the selection of data series and the method used to estimate temperatures from them.

A 1000-year long climate simulation, undertaken (by another research group) with a computer model for the physics of the atmosphere and the oceans, show large similarities with the new reconstruction. The climate in this model is governed by reconstructed variations of solar radiation and the amount of volcanic dust in the atmosphere (which reflects sun-light back into space). The fact that these two climate evolutions, which have been obtained completely independently of each other, are very similar supports the case that climate shows an appreciable natural variability - and that changes in the sun’s output and volcanic eruptions on the earth may be the cause.

This means that it is difficult to distinguish the human influence on climate from natural variability, even though the past 15 warm years are best explained if one includes human influence in the simulations. The new study underscores the importance of including natural climate variability in future scenarios. It is not only the humans that can cause appreciable climate changes - nature does it all the time by itself.

Explore further: Habitat prediction model created to protect piping plovers

Related Stories

Habitat prediction model created to protect piping plovers

July 30, 2015

Beach walkers along the East Coast often share the sand with several kinds of birds that scavenge the shore just out of the reach of waves. Among these shorebirds is the piping plover—a tiny, busy bird that nests in open ...

Researchers find reasons behind increases in urban flooding

July 27, 2015

Scientists at the University of South Florida's College of Marine Science investigating the increasing risk of 'compound flooding' for major U.S. cities have found that flooding risk is greatest for cities along the Atlantic ...

Could 'windbots' someday explore the skies of Jupiter?

July 23, 2015

Among designers of robotic probes to explore the planets, there is certainly no shortage of clever ideas. There are concepts for robots that are propelled by waves in the sea. There are ideas for tumbleweed bots driven by ...

Recommended for you

Magnetism at nanoscale

August 3, 2015

As the demand grows for ever smaller, smarter electronics, so does the demand for understanding materials' behavior at ever smaller scales. Physicists at the U.S. Department of Energy's Ames Laboratory are building a unique ...

How the finch changes its tune

August 3, 2015

Like top musicians, songbirds train from a young age to weed out errors and trim variability from their songs, ultimately becoming consistent and reliable performers. But as with human musicians, even the best are not machines. ...

Study calculates the speed of ice formation

August 3, 2015

Researchers at Princeton University have for the first time directly calculated the rate at which water crystallizes into ice in a realistic computer model of water molecules. The simulations, which were carried out on supercomputers, ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.