by Judith Curry
The climate establishment increasingly recognizes that the threat of future warming has been halved within the past five years.
Summary: The climate “catastrophe” is not what it used to be. Around 2013 with the publication of the IPCC Report AR5, RCP8.5 is considered a business-as-usual emissions scenario, with an expected warming of 4 to 5 oC by 2100. There is now a growing acceptance that RCP8.5 is implausible and that RCP4.5 is arguably the current business-as-usual emissions scenario. Just a few years ago, an emission trajectory followed RCP4.5 with 2 to 3 oC warming is considered a success of climate policy. Because the warming limit is 2 oC seems to be within reach (now considered the “threshold of disaster”),[i] the target columns were moved in 2018 to reduce the warming target to 1.5 oC. Current climate disaster rhetoric seems to involve extreme weather events, most of which are difficult to pinpoint any role in anthropogenic climate change. caused in increasing their intensity or frequency.
The mainstream media is now inundated with articles by prominent journalists about how the threat of global warming is less than we think. Here are some featured articles:
David Wallace-Wells is one of the most interesting journalists when it comes to climate space. In 2017, he wrote an article in New York Magazine in 2017 titled “The Earth is uninhabitable,” with subtitles: “Famine, economic collapse, sun scorching us: What climate change could wreak havoc — sooner than you think.” Not long after publishing his book in 2019 entitled Earth is uninhabitableDavid Wallace-Wells made this happen statement: “Anyone, myself included, who has built their understanding of how much warming is likely to happen this century for that RCP8.5 scenario should perhaps reconsider that understanding in terms of less alarming direction.” DWW scores a lot of points with me for quickly making his preliminary adjustments to the growing amount of evidence that RCP8.5 is unbelievable.
Well, the “message” surrounding the latest DWW article is that we are succeeding with emissions reductions (no, we are not). The second message is to acknowledge that warming will be less than we think, but the effects of warming will be worse than we thought (no). The third message is that advances in science have brought us to this (relatively) happy place (nope).
At the heart of this good news is the UNFCCC’s removal of RCP8.5 from the policy-making process. The hero of the science behind this abandonment is Justin Ritchie, a recent PhD. graduate (whose work has been cited in previous RCP8.5 posts at Climate Etc).
COP26 and now COP27 have quietly removed RCP8.5 (and SSP5-8.5) from their considerations, focusing on the envelope between RCP4.5 and RCP2.6. The IPCC Big Dogs don’t seem to see this coming (or prefer to keep ringing the alarm), as they have instructed climate modelers for CMIP6 to continue focusing on SSP5-8. Climate researchers continue to focus on this scenario in its impact on publications. IPCC AR6 features SSP5-8.5, although WGI made this warm statement
“In the scenario literature, the plausibility of high emission baseline scenarios such as RCP8.5 or SSP5–8.5 has been argued based on recent developments in the energy sector.”
The second so-called scientific advances are lower climate sensitive values. The so-called progress linked to the IPCC AR6 decision does NOT include values obtained from climate models (which have prevailed in previous IPCC reports). They implicitly admit that climate models are running too hot and that you can get any value of climate sensitivity you want from a climate model (which is already obvious to me). me and many others over the past decade). IPCC AR6 has reduced the upper limit of ECS to 4.0oC (from 4.5oC before); this continues to work to reduce the expected amount of warming. IPCC AR6 also increases the lower probability limit of ECS to 2.5oC (from 1.5oC). Raising the lower limit of ECS is very difficult, according to recent publications by Nic Lewis
COP27 is operating from the value of expected warming of 2.5oC in 2100. This level is said to be still too high for a number of reasons. The IPCC expert assessment rejected the lower climate sensitivity values (which should not have been rejected according to the Nic Lewis paper). Furthermore, the IPCC projections do not take into account future natural climate change scenarios. See recent posts:
X https://judithcurry.com/2022/01/23/crossing-or-not-the-1-5-and-2-0oc-thresholds/
X https://judithcurry.com/2021/11/21/solar-variations-controversy/
In addition to an insufficient number of volcanic and solar scenarios, climate models ignore most of the indirect effects of the sun and climate modeling treatment on multi-level and longer-term intrinsic variability. related to ocean circulation is not appropriate. While these elements could in principle go warmer and cooler, there are several reasons to assume that these natural elements are tilted toward cooler for the rest of the 21st century:
- Baseline volcanic activity since 1850 is unusually low
- Most solar researchers expect some sort of solar minimum in mid to late 21st century
- The indirect effects of solar energy are inadequately handled by climate models, which would work to amplify the solar cooling process.
- A shift to the cold phase of the Atlantic Multipolar Oscillation is expected over the next decade, which affects not only global temperatures but also the Greenland and ice mass balance. Arctic sea.
Once you include alternative scenarios of natural variability, the temperature change in 2100 could easily fall below 2oC and even 1.5oC. Recall that this warming is relative to the baseline for the years 1850-1900; 1.1oC warming has occurred.
Impact
David Wallace-Wells offers some “hope” for climate warningers with this sentence:
“The sad thing is that now scientists have underestimated, not overestimated, the impact of warming.”
I just don’t know what else to say here. IPCC AR6 provides very little fodder to support DWW’s claim. Apart from sea level rise, which is clearly associated with global warming, there is no prima facie reason that extreme weather events will get worse as the climate warms. Observational evidence, provided you go back to at least 1900, suggests that nearly all recent, catastrophic weather and climate disasters have precedents in the 20s.order century and therefore “detection” is very difficult. Climate models are not fit for purpose to simulate extreme weather events, let alone attribute them to man-made warming. We are then left with simple thermodynamic calculations to infer the worsening of extreme weather events, which ignore the complete dominance of atmospheric and oceanic cycles. .
Think about the impact of assuming extreme weather and extreme impacts that are sensitive to 0.5oC change in temperature. If so, this leads to the conclusion that the dominant climate factor is natural climate variability, with an annual variation of about one-tenth of a degree from El Nino and La Nina, a remarkable volcanic eruption. and/or multilayer oceanic oscillations. The rationale for ignoring natural climate variability is based on the assumption that a large amount of fossil fuel warming from climate model simulations spikes by RCP8.5 and other values. High value of ECS will affect natural climate change. Halve warming (or reduce it even further), and you’ll lose excuses for ignoring natural climate variability.
So is all of this a “win” for climate science? I do not think so. But I told you so. . .
And finally Bret Stephen’s article covers all these important figures. Do we infer that warming causes fewer deaths (there is also a correlation in ASSOCIATION)? It may be, but the real cause of this decline is growing wealth, increased warnings, and adaptation to extreme weather and climate.
Extreme weather and climate events are something that should be addressed independently of the AGW issue. The world has always suffered from extremes of weather and climate, and it always will; this will not change with further warming or with reduced emissions.
COP27
The policy implications of all of this are enormous. Unfortunately, I suspect that COP27 will focus too much on emissions reductions (which do not work and will not affect climate in any case), and not enough on supporting development and adaptation. to developing countries and, most importantly, to support development in Africa by allowing them to benefit from their fossil fuels (in addition to selling them to Europe). Concerning the latter, a recent appeal by Rose Mustiso Nature publication; Rose is my favorite African activist and thinker on the subject.
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