After dropping 5.4% in 2020, global fossil CO₂ emissions are expected to increase 4.9% [4.1-5.7%] in 2021, finishing just 0.8% below 2019 emission levels.
Coal & gas are now back above their pre-pandemic (2019) levels, while oil remains suppressed.
Assuming oil returns to 2019 levels in the next year or two, a drop in coal use is required to avoid further emissions growth.
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China grew in 2020 & especially 2021, now with solid growth since 2016.
Other major countries had a rebound which puts them back on their decade trends.
The recovery is also uneven across smaller countries (all others).
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Our projections are the hard work of @robbie_andrew & @jikorsbakken, who use monthly energy data to estimate emissions & then project forward for the months without data.
This means we have estimates by coal, oil, gas, & cement for major emitters.
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This year there was a major update of CO₂ emissions from land-use change, mainly in Brazil.
Land-use change emissions now trend downwards in the last decade instead of trending upwards in the earlier budgets (dotted line).
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In the @gcarbonproject, we update all the data every year (come on, seriously, you think we just add an extra year?).
With the new land-use data, total emissions are now flat in the last decade.
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The revised LUC data does not help keep RCP8.5 alive, unfortunately (?).
Now total CO₂ emissions are clearly deviating from high-end emission pathways (this was not the case previously).
All these CO₂ emissions lead to an increase in the atmospheric concentration of CO₂, which are estimated to reach 415 parts per million (ppm) this year.
@robbie_andrew uses available observational data & projects for the rest of the year using the seasonal cycle.
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In the last decade, the atmospheric CO₂ increase has averaged ~2.4ppm.
Even though emissions dropped 5.4% in 2020, CO₂ increased 2.4ppm.
In 2021 emissions went up 4.9%, but CO₂ may increase only 2.0ppm.
I am still pondering over 2023 & El Nino. Is 2023 an (unusual) outlier or not?
Looking at anomaly in 2023 relative to the trendline (loess 50 year window), without (left) & with (right) annualised ENSO lags, then 2023 is rather mundane.
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When looking at the temperature change relative to the previous year, without (left) & with (right) annualised ENSO lags, then 2023 is more unusual depending on the lag.
If 2023 is unusual, then it could be equally explained by 2022 being low (rather than 2023 being high).
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There are numerous ways to consider ENSO. I have used annualised indexes, & various lags can be included. It is also possible to take sub-annual indexes (eg, several months), & again, various lags.
What is statistically best? I presume there is a paper on this.
I started to take an interest in the 2023 temperature increase...
The first plot I did, to my surprise, seems to suggest that 2023 is not unusual at all (given El Nino).
Why?
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It all depends on how you slice the data. The previous figure was the anomaly relative to a trend (loess with 50 year window).
If I plot the change from the previous year (delta T), then 2023 is more unusual. Though, still, is it 2023 that is unusual, or 2022, or 2016, or?
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The loess trend changes shape with the data, making the 2023 anomaly smaller. It is also possible to use a linear trend, making the 2023 anomaly larger.
Comparing the anomaly to a linear trend will make 2023 more important (than if loess is used).
I am not so convinced. The land sink has a lot of variability, mainly due to El Nino, and an El Nino overlapped 2023. So we expect a lower land sink in 2023.
(My estimate assumes the ocean sink was average).
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Was 2023 an El Nino year? That is not so obvious...
How does one average the monthly sea surface data to an annual value El Nino index? How does one account for the lag between El Nino and the change in atmospheric CO2 growth?
There is no unique answer to this.
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This figure shows the monthly El Nino index annualised with different time lags. 2023 is an El Nino or La Nina, depending on how you average!
@richardabetts & @chrisd_jones use a 9 month lag in their work (which means 2023 was a La Nina)!
Record high emissions means record high radiative forcing.
We have you covered, we also include aerosols (SO2, etc) & have done so for decades. Also shipping!
Short-lived aerosols are important, but should not distract from the drivers of change: greenhouse gas emissions!
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Most of the energy put into the system ends in the ocean (90%), so the Ocean Heat Content (OHC) has been increasing along with emissions and radiative forcing.
This also means the Earth Energy Imbalance is also increasing.