The Difficulties of Averting Catastrophic Climate Change
9 October, 2018
So I read the Special Report on stabilizing global warming at 1.5 degrees C/2.7 degrees F by the Intergovernmental Panel On Climate Change. The report was released Sunday Night. Here are just a few takeaways.
-The hottest days over land areas will be 3 C (5.4 F) hotter at 1.5 C and 4 C (7.2 F) hotter at 2 C. and coldest days at high latitudes will be 4.5 C ( 8.1 F) warmer at 1.5 C and 6 C (10.8 F) warmer at 2 C. Heat gets much worse and cold is extraordinarily diminished.
-The duration and intensity of drought and heavy precipitation will be much worse at 2 C than at 1.5 C.
-Sea level rise is expected to be around 0.25-0.75 meters by 2100 with 1.5 C warming and around 0.1 meters high at 2 C warming.
-A 45% reduction in carbon dioxide emissions is relative to 2010 levels (58% relative to 2015 according to climate scientist Stefan Rahmstorf) is required by 2030 and with zero net emissions by 2050 and "negative emissions" afterward. Negative emission is removing carbon dioxide from the atmosphere. Assumed to remove 100-1000 gigatons of it during the remainder of the 21st century.
Now here are some things I have to say about the report.
--It does seem to come full circle in terms of acknowledging the seriousness of the lower temperature thresholds at causing more catastrophic impacts to human and natural systems on Earth. The 1990 UN Advisory Group on Greenhouse Gases discussed the 1 degree C limit and the likelihood for nonlinear responses and feedback loops to kick in once such a value was routinely reached. While obviously scientists raised the bar to 2 C then began to emphasize increasingly 1.5 C to the emphasize the needs of island and subtropical nations' concerns with regards to sea level rise and agriculture, the IPCC has acknowledged that the Earth has warmed by about 1 degree C since the mid-19th century (which is used to approximate pre-industrial temperatures).
--The mitigation efforts of the IPCC continue to be based purely on human emissions and simply neglect too many things which a) are more difficult to model but b) will likely severely detriment carbon "budgets"...the amount of carbon still considered for humans to burn into the atmosphere to keep temperatures at or below a certain temperature threshold.
Carbon emissions from land and permafrost (potentially massive)
Carbon emissions from wetlands
The IPCC does mention that these caveats in the report. Do a couple sentences count?
--As the discussion around solving climate change continues to revolve around human emissions, what perhaps few realize is that it is not only about what is being done now, but what has been done in the past. As carbon dioxide can remain in the atmosphere for hundreds to thousands of years, the effects of warming are prolonged. There is currently 410 parts per million of carbon dioxide concentration in the atmosphere plus other non-CO2 gases adding significant effects. This means in order to stabilize temperatures at 1.5 degrees C, humanity must not only reduce current emissions, but remove carbon dioxide from past emissions out of the atmosphere and store it. There must be net negative emissions.
The problem is no such technology exists at the scales required to extract a trace gas in the billions of tons and store it (learn more here). There is also the problem of the the fact that a significant amount of energy (fossil fuels) will be required to build (and perhaps power?) the infrastructure on a global scale to remove the pollution which will contribute further greenhouse gases to the atmosphere (which will need to be removed as well).
Right now, we have 410 parts per million concentration of carbon dioxide and rising, plus the rising methane and nitrous oxide (and other very small but powerful greenhouse gases) which are simply too much to stabilize global warming at 1.5 C in the long term. Or 2 C. Or 2.5 C. In fact, Dr. Peter Carter, a climate scientist based in British Columbia estimates the 2017 total greenhouse gas concentration equivalent locks in a long-term global mean surface temperature of 2.6 C (meaning without no new emissions or carbon removal).
-Global Dimming is probably the nonexistent topic in global climate change discussion, but one of the most important. Basically industrial burning produces particulates which are blown around the atmosphere and reflect solar radiation back into space, cooling the surface. Sulfates have been a major agent. Research shows that reductions in aerosols may lead to additional warming of 1-2 C (1-3 C over land areas). So reduce emissions in the process of trying to get off of fossil fuels and you end up reducing aerosols which induces further global "brightening", accelerating global warming further. And as aerosols fall out of the atmosphere within weeks to months after industrial activity ends, it ends to be a very abrupt and rapid response by the climate system in terms of temperature and precipitation.
And speaking of which, there is little discussion of the increasing potential destabilization of the weather in the climate system outside of precipitation. And sea level rise mentioned above is likely severely underestimated.
So, to conclude...as the scientists behind the report have stated...technically, it is within the laws of physics and chemistry to accomplish what is necessary to avert catastrophic climate change. However, in order for humans to fix the problem, they would need to have the technical feasibility to 1) create an entirely new energy infrastructure as rapidly as possible, 2) create an infrastructure to remove and store the the pollution of the previous energy infrastructure as rapidly as possible, 3) and do so while using the very same greenhouse gas (and other) polluting infrastructure. Based purely on what has already been done, we would expect extreme (greater than 2 C) warming, which would threaten to initiate a process toward a near-inevitable "hothouse" state as 1.5-2 C above pre-industrial is likely an "unstable" temperature state for the planet. And the instability...which, as the UN believed in 1990, may have started as low as 1 degree C, may be capable of non-linear processes which are hard to quantify.
And as a side note...the IPCC completely avoids the science of abrupt climate change because of major tipping points which can amplify warming or climate circulations in other destructive ways. However, the concept that changes can happen on very rapid timescales (years to a few decades), is well known from paleorecords. (See discussion by Dr. James Lovelock and Dr. James White). Powerful tipping points include Arctic sea ice, the Atlantic Meridional Overturning Circulation, mid-latitude jet stream, among others.
These reasons are why I tend to believe that humanity will be unable to stop climate change. Humanity will certainly try, but the cards are stacked heavily in favor of thermodynamics non-linear processes and chaotic behaviors, sadly. Beating thermodynamics usually means using time to your advantage and having graphs such as the one below, where even then, you have to suck a trace gas out of the atmosphere to win at the end, is usually not a good bet. I certainly wish ourselves much luck.
--Meteorologist Nick Humphrey