Records of carbon dioxide in the atmosphere millions of years ago support current predictions on climate change from the Intergovernmental Panel on Climate Change (IPCC) according to a new study.
New records have been analysed by a multinational research team at the University of Southampton showing the CO2 content of the Earth’s atmosphere between 2.3 to 3.3 million years ago, over the Pliocene.
The earth was around 2 degree C warmer during the Pliocene than it is today and atmospheric CO2 levels were around 350-400 parts per million (ppm), similar to the levels reached in recent years.
The scientists have been able to estimate how the climate will respond to increasing levels of carbon dioxide, a parameter known as climate sensitivity, and also show how it can vary over the long term was determined by studying the relationship between CO2 levels and climate change during a warmer period in Earth’s history.
Today the Earth is still adjusting to the recent rapid rise of CO2 caused by human activities, whereas the longer term Pliocene records document the full response of CO2-related warming as viewed by co-author Gavin Foster.
The estimates of climate sensitivity lie well within the range of 1.5 to 4.5 degrees C increase per CO2 doubling summarised in the latest IPCC report was added by Foster. Thus it can be concluded that the research community has a sound understanding of what the climate will be like as we move toward Pliocene like warmer future caused by human greenhouse gas emissions.
The findings of this study have been published in Nature.