A few days ago the journalist and author Peter Hitchens tweeted out his doubts about the actual cause of climate change. The observed warming was not in doubt, it is the “why” that he questions …
Like you @barumdean , I have no idea what the cause may be. I’ll wait for someone using the scientific method to come up with a testable, faisifiable proposition. Unlike you, I don’t pretend to know. You mustn’t think everyone’s like you.
In fact, here is that tweet so that you may check it in context …
To repeat, and to be wholly clear here, his position is not a rejection of the observed warming, but rather is a rejection of the prevailing scientific consensus that the primary cause is human activity …
This is incorrect in numerous ways. For example, he is wrong about the claim that “Nobody Disputes warming”. There are in fact people who do dispute the observed warning. They are wrong, but that’s a different argument.
Putting that aside, Peter’s claim is that it is zealots that attribute it to humans and that holding the position that humans are responsible is not scientific. Again wrong. There is robust testable, falsifiable science behind the consensus that humans are responsible.
Humans and Warming: How do we know this?
The point of this posting today is not to highlight just one guy, but rather to use the stance being taken as reason to explain why we now know what we know, and why it is the prevailing consensus.
Others seeing the above did respond to Peter. One of the very best rebuttals comes via Gavin A. Schmidt. He is a climatologist, climate modeler and Director of the NASA Goddard Institute for Space Studies (GISS) in New York. He is also the co-founder of the award-winning climate science blog RealClimate. In other words, what follows are the words of a subject matter expert.
The full thread of his response starts here …
However, for those not on twitter, or for those who find the process of jumping from tweet to tweet to glean the information a tad tedious, I’ve pulled it all out for you into one easy-to-read digestible form (blue text so that it is clear that they are Gavin’s words, not mine) …
Since this comes up a lot, a quick run though of the testable, falsifiable, science that supports a human cause of recent trends in global mean temperature.
First off, we start with the observations:
- spectra from space showing absorption of upward infra-red radiation from the Earth’s surface.
- Measurements from around the world showing increases in CO2, CH4, CFCs, N2O.
- In situ & space based observations of land use change
We develop theories.
- Radiative-transfer (e.g. Manabe and Wetherald, 1967)
- Energy-balance models (Budyko 1961 and many subsequent papers)
- GCMs (Phillips 1956, Hansen et al 1983, CMIP etc.)
We make falsifiable predictions. Here are just a few:
- 1967: increasing CO2 will cause the stratosphere to cool
- 1981: increasing CO2 will cause warming at surface to be detectable by 1990s
- 1988: warming from increasing GHGs will lead to increases in ocean heat content
- 1991: Eruption of Pinatubo will lead to ~2-3 yrs of cooling
- 2001: Increases in GHGs will be detectable in space-based spectra
- 2004: Increases in GHGs will lead to continued warming at ~0.18ºC/decade.
We test the predictions:
Stratospheric cooling? ✅
Detectable warming? ✅
OHC increase?✅
Pinatubo-related cooling?✅
Space-based changed in IR absorption? ✅
post-2004 continued warming?✅
With this validated physics, we can estimate contributions to the longer term trends. –
We can also look at the testable, falsifiable, theories that were tested, and failed.
Solar forcing? Fails the strat cooling test.❌
Ocean circulation change? Fails the OHC increase test ❌
Orbital forcing? Fails on multiple levels ❌
If you have a theory that you don’t think has been falsified, or you think you can falsify the mainstream conclusions, that’s great! We can test that too! (But lots of people have tried this already so expect there to be an answer already).
PS. Actually, it’s even a bit harder. Not only would you need to find a theory that does as well as the current theory, but you’d also need to show why the current theory isn’t operative.
Is Peter Hitchens being Stupid?
It is perhaps more than a tad simplistic to simply say “yes” to that.
Part of the human experience is that we all often latch on to ideas and beliefs for what can best be described as emotional reasons. We need something to be true, we want it to be true, so we conclude that we are not wrong and that it is true. To one degree or another we all tend to do that, is is a natural outcome of how we function.
The beauty of the scientific method is that it has granted us insights into the things that are actually true because it is a process that recognises that we often successfully fool ourselves.
With the scientific methodology, we make observations. We then come up with an idea that explains the observation. It needs to be a full and complete explanation that accounts for everything and it also needs to be testable. If it fails the test then the idea is wrong and that conclusion remains true no matter how smart or how beautiful the idea is. It also remains wrong no matter who said it. It even remains wrong if everybody still believes it to be right.
When a testable explanation withstands all objective tests then, and if you are interested in believing as many true things as possible, then it is your best bet.
- Vaccines really do work and do not cause autism
- There is no bigfoot
- Aliens are not kidnapping befuddled individuals in rural areas on their way home from a bar and sticking probes up their butts
- 9/11 was not a controlled demolition and inside job
- etc…
To jump back on topic – yes the world is warming, that is an observable fact.
We now also know why, and we understand that it is us. There are very good robustly tested reasons for such a conclusion. Until somebody comes up with a better explanation then accepting the prevailing scientific understanding is the very best conclusion available.
Will Peter change his mind?
Probably not. He is too deeply emotionally invested in his current stance.