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High concentration of CO2 in atmosphere by 2025

Date: 15 July 2020 Tags: Climate Change

Issue

By 2025, atmospheric carbon dioxide (CO2) levels will very likely be higher than they were during the warmest period of the last 3.3 million years, according to new research.

 

Background
The team studied the chemical composition of tiny fossils, about the size of a pinhead collected from deep ocean sediments of the Caribbean Sea to arrive at the conclusion.

 

Details

  • Scientists used data from chemical composition to reconstruct the concentration of CO2 in Earth's atmosphere during the Pliocene epoch, around 3 million years ago when our planet was more than 3°C warmer than today with smaller polar ice caps and higher global sea-levels.

  • Knowledge of CO2 during the geological past is of great interest because it tells us how the climate system, ice sheets and sea-level previously responded to the elevated CO2 levels

  • To determine atmospheric CO2, the team has used the isotopic composition of the element boron, naturally present as an impurity in the shells of zooplankton called foraminifera or 'forams' for short.

  • These organisms are around half a millimetre in size and gradually accumulate in huge quantities on the seabed, forming a treasure trove of information on Earth's past climate.

  • The isotopic composition of the boron in their shells is dependent on the acidity (the pH) of the seawater in which the forams lived.

  • There is a close relationship between atmospheric CO2 and seawater pH, meaning past CO2 can be calculated from careful measurement of the boron in ancient shells.

  • They found that the warmest part of the Pliocene had between 380 and 420 parts per million CO2 in the atmosphere.

  • This is similar to today's value of around 415 parts per million, showing that we are already at levels that in the past were associated with temperature and sea-level significantly higher than today.

  • Currently, our CO2 levels are rising at about 2.5 ppm per year, meaning that by 2025 we will have exceeded anything seen in the last 3.3 million years.

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