A couple of points: 1. ESCIMO is “just” a model and could be wrong (and many climate scientists think it is wrong) 2. We will have passed the “point of no return” if the annual change in radiative forcing from anthropogenic emissions and natural feedbacks is significantly greater than zero for an extended period time (i.e., if the atmospheric CO2e PPM continues to increase at a “significant rate” after anthropogenic emissions are eliminated). 3. To avoid “passing the point of no return” we need to not only reduce anthropogenic emissions to zero but also remove CO2 from the atmosphere to compensate for the emission-equivalents from natural feedbacks. 4. The major “unknowns” a. How fast we will likely mitigate our emissions b. The cost/ton to remove CO2 from the atmosphere c. How much we willing to pay to remove CO2 from the atmosphere d. The expected annual CO2 emission-equivalents from natural feedbacks e. Climate sensitivity 5. We cannot say definitely that we have not “passed the point of no return” but neither can we definitively say that we already have (or will have at a specified time in the future) 6. But some signs from recent articles are very troubling: a. Loss of summer Arctic Sea ice could contribute an extra 0.19°C of global warming around mid-century b. Nitrogen fertilizers are jeopardizing agricultural climate goals c. New Study Shows a Vicious Circle of Climate Change Building on Thickening Layers of Warm Ocean Water d. Cloud shapes and formations impact global warming – but we still don't understand them e. Warming of 2 C would release billions of tons of soil carbon f. Most surprising thing about a new report showing climate change imperils the US financial system is that the report even exists g. Nobody said going to all renewables would be cheap or easy h. ‘Staggering’ rise in climate emergencies in last 20 years, new disaster research shows 7. See the email below for additional insight

Given so many uncertainties, the only viable option is to work as hard as possible to mitigate emissions ASAP and to hope that future generations will be willing to pay for significant removal of CO2 from the atmosphere. Catastrophic sea level rise is inevitable and our civilization will likely survive as long as climate change does not drastically impact our agricultural system.

Re: [CDR] Self-sustained melting of permafrost even if all man-made GHG emissions stop in 2020 From: Bruce Melton -- Austin, Texas [bmelton@earthlink.net] Sent: Sun 11/15/2020 11:02 AM Natali's modeling of 2003 to 2017 permafrost emissions supports Randers et al. --linked below. You all know that science is reticent, climate science more so than others, and slamming nascent findings is high sport in some academic circles. If climate scientists could have told us 30 years ago, that even if we were able to slow our emissions that tipping would still initiate with less than 1.0 C warming above normal instead of the 5 C tipping suggested up until the 1.5 C Report, and that no further warming above 1.0 C would complete those tipping initiations, and that some of the tipping was irreversible and would cause nearly half of other tipping systems to cascade, what would we as a global culture have done? The science that said these things was present 30 years ago, and even more so 20 and 10 years ago, but it was nascent. The same arguments were made back then about dystopian scenarios that are being made today about the finer points of individual Earth systems collapse driven climate tipping. Our climate policy must be based on risk and resulting failure scenarios. Risk of Covid death is far higher in older patients and even higher in older diabetic patients. After 30 years of delay, Earth is an older diabetic patient. Climate science has very poor safety factors. IPCC's net-zero 2050 has a 50/50 chance of failure. Net-zero 2040 has a one in three chance of failure. Insurance standards however, that our culture has decided are what we can count on to keep us safe, allow a failure rate of one in one-hundred, or the 100-year event. I am not saying I support Randers et al., I am saying I came to the same conclusion in 2018 on our 16,000 mile filming odyssey across North America, with no modeling, where we found permafrost collapse hundreds or even thousands of times more numerous than when we filmed in 2007. In 2019 this conclusion was made irreversible by Natali 2019, and several other permafrost collapse findings. Why permafrost is collapsing is because of the heat of fusion. It takes 289 times more heat to melt ice into water, to change the state of H20 from solid to liquid, than it does to change the temperature of ice the same amount and have it remain as ice. Permafrost is collapsing today because the latent heat of fusion has been completely invested in the ice that is collapsing. This is a classic physics tipping point, where tipping is initiated with warming above the steady state and concludes when 289 times more warming has been invested. To stop the collapse, the best way, is that we simply need to remove the perturbation, nothing more. Removing the perturbation means removing GHGs from our atmosphere to bring back permafrost's former equilibrium climate. There may be some amount of climate change that is warmer than the range of temperature of our old climate, but do we have the time to figure this out and still act? Natali et al., Large loss of CO2 in winter observed across the northern permafrost region, Nature Climate Change, October 21, 2019. https://www.uarctic.org/media/1600119/natali_et_al_2019_nature_climate_change_s41558-019-0592-8.pdf Natali et al., say 2.3 Gt average CO2 emissions annually from permafrost 2003 to 2017 with no quantification of methane. Here's the important bit: if permafrost was stable and not emitting in 2003, and it was probably stable or not far from stable, if the 14-year average annual is 2.3 Gt CO2, the emissions today are far in excess of the 14-year average, likely double or more. Climate Change Across America, Inglorious Events (2019, 45 minutes) Cheers, B

Bruce Melton PE Director, Climate Change Now Initiative, 501c3 President, Melton Engineering Services Austin 8103 Kirkham Drive Austin, Texas 78736 (512)799-7998 ClimateDiscovery.org MeltonEngineering.com