Global warming is settled science, but what does that mean?
Global warming is settled science, but what does that mean?
It’s real, it’s serious and it’s caused by us, but there is still variance to address
One of the regular back and forths between people who accept the science of global warming and climate change and those who are ‘skeptical’ of it is the question of whether it is settled or not. This isn’t helped by the completely reasonable communication around nuanced and complex topics by scientists in which they are careful to say what we don’t know, how much is still to be learned and to caution over-reliance on any single result.
But the science of global warming and climate change is settled in the most part, and the parts where it isn’t are almost entirely a matter of degree not of kind. The relatively minor uncertainty is picked up by the ‘skeptics’ who claim that they are defending science and the conservative post-modernists
Let’s talk about what ‘settled’ means and which parts of climate change are more and less settled.
Settled means that barring a major paradigm shift in fundamentals of science per Kuhn’s The Structure of Scientific Revolutions that something is not going to change. Settled means that enormous swaths of science are based upon this paradigm. Settled means that scientists assume it is true as they move forward with hypotheses and experiments related to implications of the settled science.
What are some examples of settled science? Gravity. E = mcˆ2. Tobacco kills. Vaccination prevents major communicable diseases. Global warming is real, serious and caused by humans. Climate change due to global warming is real and serious.
Let’s look through the different aspects of global warming and climate change and see which are settled 100%, which have some degree of variance outstanding and if so how much.
CO2 traps infrared leaving the Earth, increasing the temperature of the atmosphere. 100% settled.
Methane also traps infrared, in much higher amounts than CO2 but dissipates from the atmosphere much faster. 100% settled.
Humans have increased CO2 in the atmosphere by 67% in the past couple of hundred years. 100% settled.
If CO2 and methane double (which we are closing in on) that locks in 1.0 to 1.2 degrees Celsius or 1.8 to 2.2 degrees Fahrenheit of warming. 100% settled, but note the range of uncertainty. This depends on all of the previous pieces.
There is a feedback factor with water vapor. More warmth in the atmosphere means more water vapor and water vapor traps even more heat. If CO2 and methane double — once again, closing in on this — then the feedback with water vapor results in an additional 1.6 degrees of warming. This is 100% settled within a slightly larger range of possibility. This depends on all of the previous pieces.
There is a feedback factor with clouds which has a wider range of possible results in the models, from 0.3 degrees to 1.1 degrees with 0.7 degrees being the median. That cloud feedback will increase warming is 100% settled, but the range of the feedback is of lower certainty. This depends on all of the previous pieces.
There is a conservative median likelihood given the above of 60 centimeters or two feet of sea level rise by 2100 if we merely stopped adding greenhouse gases to the atmosphere extremely rapidly. There’s a fair amount of variance on this, almost all of which is on the really bad side, with news every day of new ice shelfs dropping into the sea and feedback effects eliminating more ice currently on land much more rapidly than expected. The science on sea level rise certainly isn’t settled except for one part: there is 100% certainly that the sea will rise substantially, it’s just a question of whether it’s a meter or several meters and whether it’s in 80 years or 150 years. That depends on all of the previous pieces.
Extreme weather events will increase. That means more droughts, tornadoes, hurricanes, monsoons, floods and the like. That’s 100% settled. The degree of increase and the actual numbers vary widely. Where the impacts will be most felt varies substantially. The degree of impact is not settled, but not the basics. That depends on all of the previous pieces.
The impact on species, humans, disease spread and the like is almost entirely negative due to the rapidity of change. That’s 100% settled. How severe the impacts will be and where they will be felt specifically has greater variance. That depends on all of the previous pieces.
There is a core of 100% settled science at the heart of climate change which will not change unless there is a huge paradigm shift in our understanding of the climate, something which is extremely unlikely. None of the precursors Kuhn identified to a paradigm shift are actually apparent in the literature and research that is underway. Agreement based on multiple studies using different methods and data set is increasing — that’s consilience — and scientific consensus is emerging around the edge conditions.
Overall, the IPCC, a highly scrutinized, highly politicized body which has produced a very conservative, nuanced and rigorous perspective sees 95% certainty of significant, serious, human-caused climate change. This isn’t 95% certainty of humans causing global warming, that’s 100%.