Thread by @richardabetts

We predict that in 2019, the annual mean CO2 concentration at Mauna Loa will be 411.3 ± 0.6 ppm

This is 2.75 ± 0.58 ppm higher than 2018 - a larger rise than most years in the record including the last two years, but not as large as 2015-2016

metoffice.gov.uk/news/releases/…

The relatively large rise is due to record high anthropogenic CO2 emissions and a temporary weakening of land carbon sinks due to climate variability.

The record rise in 2015-2016 was due to the sinks being particularly weakened by the large El Nino event at that time.

Here's the Guardian's article on our CO2 rise forecast.

theguardian.com/environment/20…

Our forecast is based on a correlation between annual CO2 rise & sea surface temperatures in the preceeding April-March. The recent warm period in the tropical Pacific suggests a faster CO2 rise.

Here's the Independent.

An important point is that this illustrates the role of carbon cycle feedbacks in the climate system. Natural carbon sinks have kept the historical rise to half of what it could have been.

But what if climate change weakens them?

independent.co.uk/environment/co…

Annual mean CO2 concentration at Mauna Loa will be above 410 ppm for the first time in 2019. It will probably be above this in all months except August, September and October, peaking at 414.7 ± 0.6 ppm in May, dropping to 408.1 in Sep then rising again.

newscientist.com/article/219188…

Here's our predicted monthly CO2 concentrations for 2019.

Last year's annual maximum monthly concentration of 411.3 ppm (May 2018) will probably be exceeded by March this year (412.0 ± 0.6 ppm)

Our forecasts of the annual mean CO2 concentration at Mauna Loa and its rise from the previous year have been successful since we started doing them 4 years ago.

We correctly predicted the record rise in 2015-16 due to influence of the large El Niño, & the slower rises since.

We use a statistical relationship between the atmospheric CO2 rise and sea surface temperatures in the Niño3.4 region of the tropical Pacific.

Applying this method in the past (red) reproduces the observed year-to-year variability of the annual CO2 rise (black) quite well.

To make the forecast we use SSTs from observations for recent months & a forecast from a climate model for coming months. We also use the previous year's emissions.

Our original prediction of the record CO2 rise in 2015-16 was published in @NatureClimate nature.com/articles/nclim…

Here's an open access version nature.com/articles/nclim…

We've also published a paper verifying our 2015-16 CO2 forecast

royalsocietypublishing.org/doi/full/10.10…

In that we also estimated that the El Niño increased the annual CO2 rise that year by about a third. This all illustrates the importance of carbon cycle feedbacks in the climate system.

That last paper was part of a very interesting special issue of Philosophical Transactions of the @royalsociety editted by @ymalhi and colleagues.

Loads of great papers documenting the impact of the 2015-16 El Niño on ecosystems & the carbon cycle!
royalsocietypublishing.org/toc/rstb/373/1…

You can track how our CO2 rise forecast is performing by checking CO2 measurements at Mauna Loa taken independently by the Scripps Institute for Oceanography scripps.ucsd.edu/programs/keeli… (tweeted by @Keeling_curve) & NOAA

We are forecasting the Keeling Curve
esrl.noaa.gov/gmd/ccgg/trend…

For regular updates on CO2 measurements at Mauna Loa, follow @Keeling_curve and @CO2_earth

https://twitter.com/CO2_earth/status/1087775711245537280