By Ben Kritz, Manila Times
January 18, 2024 70
WE are not yet three weeks into 2024, and already there have been two unexpected pieces of incredibly bad news on the climate change front. The first was the global temperature data for 2023 from the EU Copernicus program, which showed that crossing the "red line" limit of a 1.5-degree Celsius increase in global temperatures over the pre-industrial average is not, in fact, something that is five or six years in the future but is already happening. The second was a nasty surprise in the form of a research study published on January 2, which revealed that the world's soils, long assumed to be an important carbon dioxide (CO2) absorber, are actually releasing CO2 into the atmosphere at a frightening rate.
The study entitled "Projected soil carbon loss with warming in constrained Earth system models" was led by researchers from the Chinese Academy of Sciences and published in the journal Nature Communications. It is accessible online without a subscription — a bit of a rarity, in that respect — at https://www.nature.com/articles/s41467-023-44433-2. It is not a long paper, but it is rather heavy reading, so I'll provide a simplified explanation.
Soil absorbs CO2 in considerable quantities from dead plant matter; all of the CO2 taken in by trees, grasses and other plants is carried into the ground when leaves and branches fall, harvested crop plants are tilled under, and so on. The CO2 is eventually released through microbial action as bacteria and other microorganisms break down the plant matter, but it is a slow, gradual process; the soil takes in much more CO2 than it releases over any given period of time.
Or that's what climate scientists have assumed, based on experimental data done years ago; this assumption, in the form of average rates of soil CO2 absorption, has found its way into most climate models. From those models, we get our estimates of the rate of CO2 buildup in the atmosphere, the rise in global average temperature as a result, and the "carbon budget" — the amount of CO2 mankind can still emit before temperature thresholds such as +1.5 C or +2.0 C would be exceeded.
Unfortunately, the latest research has demonstrated the assumption is dead wrong and did so by gathering real-world data from soil samples taken at 366 sites around the world, covering all the various types of landscapes: different types of forests, grasslands, wetlands, croplands, tundra, and so on. The new data thus provided a "constraint" to the climate models, observed data that could be substituted for the older, mostly assumed soil CO2 absorption and release factors.
The results were not good. In the current climate models based on what could be considered a reasonably likely "average" scenario — mild to moderate global warming of something like 1.5-2.0 C, or in other words, the current aspirational goal of most climate policy — it is assumed that soil absorption would remove about 30 billion metric tons of CO2 from the atmosphere by the end of the century. Plugging the new data into the models, however, completely reverses that, showing that CO2 "turnover" will actually release about 19 billion metric tons of CO2 over the same time span.
The most important immediate consequence of this is that it means that the "carbon budget" is an overestimate by about 66 percent. Until now, the carbon budget was six years, meaning that we could continue to emit CO2 into the atmosphere at the current rate for only another six years before the 1.5 C limit is exceeded (for the mostly political purposes of the 2015 Paris Agreement, the limit is considered as a 10- to 20-year average, rather than a point). With the latest findings, that deadline has been cut to two years.
It gets worse, however; that new estimate does not take into account the latest Copernicus temperature data, which showed that Earth's temperature actually stepped over the line — or at least stepped right on it — last year. Global average temperatures for all of 2023 were 1.48 C above the 1850-1900 average, and the temperature on every day of the year was at least 1.0 C above that average, with more than 180 days exceeding 1.5 C over the average. Two days in November exceeded +2.0 C over the pre-industrial average, and November's average temperature was 1.69 C over the pre-industrial average for the month. December was even warmer, at +1.78 C.
Ironically, or perhaps not, the current temperature trajectory is very close to that predicted by climate research conducted — and kept secret from the public for decades — by the petroleum industry's CO2 and Climate Task Force in 1980. That research, which has so far been demonstrated to be extremely accurate in other contexts, predicted a 2.5 C temperature rise by 2038.
The scientists who conducted the recent soil research also pointed out that warmer temperatures will tend to accelerate soil CO2 release. The soil microbes that release the CO2 trapped in plant matter as they go about their little microbe business thrive in warmer conditions, and so the "most plausible" estimate of 19 billion metric tons of CO2 added from soil emissions by the end of the century could be as high as 45 billion metric tons.
I suppose the natural question at this point is, "What now?" Don't ask me, man, I just work here. But I do think these latest findings are a further call, nay, imperative demand for climate advocates, policymakers and institutions to pull their heads out of the clouds, resign themselves to living in the present day, and dispense with the laughably, desperately outdated messaging that "we need to take action to keep global warming under 1.5 C before it's too late." It's already too late, and has probably been too late for a long time.
