Climate tipping effects may be kicking in
For those tracking the state of the climate, the report published by the BBC showing that tropical forests were being destroyed at the fastest recorded rate over the last year, was frightening, with the prospect of total forest dieback and "savannisation" of these areas is a growing risk.
Compounding the loss of old-growth tropical forests in 2024 (estimated to have covered an area as large as Ireland) and the release of their carbon stores, is the loss of the moisture and climate systems maintained by those forest ecosystems, which previously provided localized cooling effects, produced cloud cover and contributed to the atmospheric moisture necessary for rain. These had also helped to brighten the earth, thereby reflecting more of the sunlight that otherwise would cause heating. This moisture and water cycle activity gets destroyed along with the trees, plants and animal life. This climatic loss to broad areas may be having more of a negative feedback effective on the planet's overall warming than has previously been recognized.
Global Surface Temperature Change (published 2/3/25)
This news add yet more data to the alarming report published in February by Dr. James Hansen, Dr. Pushker Kharecha and a team of sixteen other climate scientists plainly titled "Global Warming Has Accelerated: Are the United Nations and the Public Well-Informed? In it, Dr. Hansen's team explains that global temperatures have leaped up more than a half degree (0.7°F or 0.4°C) over the last 2 years, with a total average temperature rise of +1.6°C relative to the temperature at the beginning of last century (the 1880-1920 average). This reflects a temperature rise over the +1.5°C (or 2.7°F) level that we set as our goal for maximum increase. As of the last year, we've already exceeded that level.
These increases have, according to Hansen, baffled Earth scientists, as the increase's magnitude was literally off the charts. There were multiple explanations presented as to what could have caused such a big increase. Declining aerosol pollution was seen as a key contributor, by reducing nuclei that aided cloud formation and thus reflection of sunlight, thereby effectively darkening earth and allowing more heat to be absorbed. These are very troubling and portentious changes that may, in fact, show that feedback effects are already accelerating the heating impacts of our CO2 emissions, such that they no longer follow a direct relationship.
Dr. Hansen's report received considerable criticism both because it departed scientifically from the mainstream's more conservative consensus of a lower rate of warming and climate "sensitivity," as determined by the IPCC, and because it called for "a complement to the IPCC approach" to "avoid handing young people a dire situation that is out of their control." In a response to some of that criticism, Drs. Hansen and Karecha decried the ad hoc opinions, ad hominem attacks and sense that the media has gravitated towards reporting the opinions of just a small handful of scientists, rather than covering the total community and range of analyses, including their own.
Dr. Anatassia Makarieva, an atmospheric physicist, responded to this debate with a substack post titled "On the scientific essense of Dr. James Hansen's recent appeal." In it she agreed with Drs. Hansen and Karecha that many scientists were understating the degree of climate forcing but also shared her sense that many of the climate models in use, including Dr. Hansen's, erroneously ignored the major role of the biosphere in the climate destabilization that we are now experiencing. Which may, she argued, partially explain why none of the models predicted the heat anomaly of the 2023 - 2024 time period. Dr. Makarieva writes:
Why is this [i.e. accurate climate models] so important? Unless external causes of this recent temperature anomaly are identified, we may be dealing with a self-reinforcing process — for example, of reduced cloud cover causing more warming, this warming causing even less clouds and so forth until something truly ugly happens to our planet. But, if so, such a process could be started by many factors and does not necessarily need CO2 to kick off. For example, deforestation-induced reduction of evapotranspiration in the Amazon is associated with extreme heat events. This alone could trigger the warming that could then self-amplify via cloud (or some other) feedbacks.
Whether or not we have permanent self-reinforcing amplification happening with the climate now is being debated, partially thanks to new voices like Dr. Makarieva's, entering the field. What is clear, however, is that the fewer clouds, aerosols, snow cover, sea ice and also more invisible sources of water vapor (such produced by tropical forests and other natural ecosystems) the darker the earth is and the more sunlight gets through and heats the ground, the oceans and the air. This heating further impacts existing vegetation, ice sheets, permafrost and bodies of water negatively, which then also contribute more CO2, more fires, and further darkening of earth's surface. Earth's climate has been in a state of equilibrium for eons. Given what is happening with the climate now, it appears that it is leaving that state of equilibrium.
According to some reports, the Earth has "dimmed" by 0.5% in the past 25 years. We've known this and scientists have been able to track decreases in sea ice at the poles, a major factor in global warming. We're now seeing the climate effects of reductions in aerosols (due to the shipping industry trying to clean up their act and emit less aerosols), and we're seeing reduced cloud cover. The bottom line is that even just looking at cloud feedbacks, the more the climate warms, the fewer the clouds. The fewer the clouds, the more the planet warms. This feedback loop is enough to take us into very dangerous territory. Which is yet another reason why we want to prevent the loss of tropical forests, not just because of the CO
2 impacts but because of the cloud and water vapor impacts. This feedback loop could explain why the rate of heating of the planet has increased beyond what was expected, even by scientists like
Zeke Hausfather and James Hansen.
Dr. Hansen continues to urge immediate action and has proposed that "a multitude of actions are required within less than a decade to reduce and even reverse Earth’s energy imbalance for the sake of minimizing the enormous ongoing geoengineering of the planet; specifically, we will need to cool the planet to avoid consequences for young people that all people would find unconscionable."
References:
BBC, Tropical forests destroyed at fastest recorded rate last year, by Mark Poynting and Esme Stallard, May 20, 2025.
Columbia University, Climate Science, Awareness and Solutions, "Global Warming Has Accelerated: Are the United Nations and the Public Well-Informed?, published in Taylor & Francis, February 3, 2025 by James E. Hansen, Pushker Kharecha, Makiko Sato, George Tselioudis, Joseph Kelly, Susanne E. Bauer, Reto Ruedy, Eunbi Jeong, Qinjian Jin, Eric Rignot, Isabella Velicogna, Mark R. Schoeberl, Karina von Schuckmann, Joshua Amponsem, Junji Cao, Anton Keskinen, Jing Li, and Anni Pokela
Biotic Regulation and Biotic Pump Substack, "On the scientific essense of Dr. James Hansen's recent appeal." by Dr. Anatassia Makarieva, an atmospheric physicist, May 19, 2025.
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