A consensus is emerging from the results of a recent round of improved climate models: we are in very serious trouble, and may already be past the point of no return.
There is a growing realization that existing climate modeling by the IPCC and other organizations has been too conservative, focusing only on the best-understood (mostly linear) mechanisms of climate change and leaving out, or downplaying, the effects of non-linear mechanisms like feedback loops. The emerging conclusion from the newer, more robust models and interpretations, is that warming and its attendant changes like sea level rise will occur faster than has been predicted, and indeed that we may already be past the point of no return, with existential threats to civilization already occurring within a few decades (by 2050).
TruthOut has a piece which discusses the imminent new findings, and explains that more data and improved models are combining to give a new, more detailed (and more frightening) picture of the trajectory of warming over the next decades:
The title refers to the recent IPCC warning that humanity only has about 12 years for global warming to be kept at a maximum of 1.5°C, beyond which the risks of drought, floods, and other outcomes affecting hundreds of millions of people will be unavoidable. As concerning as that conclusion was, it might have understated the risk.
As TruthOut explains, a new IPCC report due out in April 2021 will contain disturbing new findings. The dramatically worsened projections are based, in part, on incorporating a higher climate sensitivity into the new round of models. This increased sensitivity, though not completely understood yet, is based in part on newly available data:
The new science that so radically increases danger over what we thought was radically dangerous before includes more modeling institutions, more models, more experiments and more data. It is now 65 percent complete. Final results will include up to 50 petabytes of results. How big is a petabyte? It would take 170 years of watching back-to-back HD movies for 365 days a year and 24 hours a day to equal 50 petabytes of information.
The buzz on this new modeling is about climate sensitivity. Climate sensitivity is how much Earth warms with a doubling of CO2 in our atmosphere, or what warming to expect when all Earth systems come into balance with 560 parts per million (ppm) CO2 — whenever this happens
Climate sensitivity in the 2007 IPCC report was 2-4.5°C. In the latest IPCC climate sensitivity report in 2013, this changed slightly to 1.5-4.5°C. Both give a best estimate of basically 3°C. Of the new modeling, preliminary results show eight out of the 13 models, with this latest most robust round of modeling ever coming in with a best estimate of 5°C or more climate sensitivity — an astonishing finding that modelers are challenged to explain.
These new predictions significantly impact our understanding of what actions must be taken, and in what timeframe, to limit warming to a non-catastropic level.
A new report by the Breakthrough National Centre for Climate Restoration in Australia presents similar findings, and concludes that massive, irreversible effects of warming might occur by 2050:
An important topic in the above report is "Scientific Reticence". The authors include a brief but very informative discussion of the problem, writing that,
Climate scientists may err on the side of “least drama”, whose causes may include adherence to the scientific norms of restraint, objectivity and skepticism, and may underpredict or down-play future climate changes.2 In 2007, security analysts warned that, in the two previous decades, scientific predictions in the climate-change arena had consistently underestimated the severity of what actually transpired.
This problem persists, notably in the work of the Intergovernmental Panel on Climate Change (IPCC), whose Assessment Reports exhibit a one-sided reliance on general climate models, which incorporate important climate processes, but do not include all of the processes that can contribute to system feedbacks, compound extreme events, and abrupt and/or irreversible changes.
They, too, conclude that change is happening faster than predicted, and that we have even less time to act than the IPCC findings indicate. In particular, "the recent IPCC 1.5°C report, which projected that warming would continue at the current rate of ~0.2°C per decade and reach the 1.5°C mark around 2040. However the 1.5°C boundary is likely to be passed in half that time, around 2030, and the 2°C boundary around 2045, due to accelerating anthropogenic emissions, decreased aerosol loading and changing ocean circulation conditions."
The report presents a 2050 scenario which includes:
- widespread ecosystem collapse (coral reefs, Amazon rainforest, and others)
- sharp decreases in water availability in the most affected parts of the world
- significant drops in food production to a level no longer adequate to feed the global population, causing skyrocketing food prices
- the possibility of human civilization coming to an end
These new findings rule out the possibility of a managed transition to a lower-emissions regime. Only with rapid, dramatic reductions in emissions (which look increasingly unrealistic given the lack of political consensus and the disastrous retrenchment of US climate policy under Trump) can we hope to avoid disaster scenarios. Those scenarios look increasingly unavoidable.