WMO Greenhouse Gas Bulletin notes CO2 emissions reach record high

Over the last eight glacial/interglacial cycles CO2 varied between 180 and 280 ppm. In comparison in 2016, CO2 concentrations were 403.3 ppm globally.

Graph of CO2 emissions from WMO bulletin.
Reconstructions of CO2 from proxy data: boron isotopes (blue circles), alkenones (black triangles) and leaf stomata (green diamonds). Direct measurements from Antarctic ice cores and modern instruments (pink). Future estimates include representative concentration pathways (RCPs) 8.5 (red), 6 (orange), 4.5 (light blue) and 2.6 (blue)

Nancy Bertler along with colleagues from GNS Science; Richard Levy and Jocelyn Turnbull, contributed a paleo-perspective to the 2017 WMO Greenhouse Gas Bulletin – State of the Greenhouse Gases in the Atmosphere Based on Global Observations. Ice core records reveal that over the last eight swings between glacials and interglacials atmospheric carbon dioxide (CO2) varied between 180 and 280 parts per million (ppm). In comparison in 2016, anthropogenic greenhouse gas emissions raised atmospheric concentrations of CO2 to a new record level of 403.3 ppm globally.

We have to look back 3-5 million years ago to find a time in Earth’s history with similarly high CO2 concentrations. Then, global mean surface temperatures were 2-3°C warmer than today, the Greenland and West Antarctic ice sheets had vanished and even parts of the low lying basins of East Antarctic ice had retreated. This caused global sea level to be 10-20 metres higher than today. But how quickly did greenhouse gas concentrations change in the past? High resolution ice core records from high snow accumulation regions in West Antarctica along with a new generation of ice cores – horizontal ice cores where old ice lays close the surface – along with new analytical techniques provide exciting insights into how quickly atmospheric CO concentrations can change.

Today’s decadal rate of about 2.2 ppm per year is 20 times faster than the come. 15-17 million years ago, CO2 concentrations were between 400-650 ppm, with global mean temperatures 3-4°C higher than today and global sea level up to 40 metres higher during the warmest periods. With the world aiming to reduce greenhouse gas emissions in accord with the UNCCC Paris Agreement, these treasurable windows into the past caution us to double our efforts.

For more information contact: Nancy Bertler