“We think that this is the most extreme version and it’s not based on facts … It’s not data driven. We’d like to see something that is more data driven. It’s based on modeling, which is extremely hard to do when you’re talking about the climate.”
–White House press secretary, Sarah Huckabee Sanders, speaking at a White House press briefing Tuesday about the Trump Administration’s assessment of the Trump Administration’s recently released climate report
Wow! If that’s true, it’s no wonder President Trump doesn’t “believe it!”
Well, gee, let’s just have a look at that over the next few days, shall we? After all, the report is publicly available:
11/28/2018
Claim: Global climate is changing rapidly compared to the pace of natural variations in climate that have occurred throughout Earth’s history. Global average temperature has increased by about 1.8°F from 1901 to 2016, and observational evidence does not support any credible natural explanations for this amount of warming; instead, the evidence consistently points to human activities, especially emissions of greenhouse or heat-trapping gases, as the dominant cause.
–Volume II, Chapter 2: Our Changing Climate, Key Message 1
Data: Oh, look, here’s some! It’s right at the beginning of Chapter 2!
The black line in the graphs is made up of the average values of the global temperature measurements from thermometers scattered around the globe. Numbers from measurements are what we refer to in science jargon as “data.” (I’ve discussed the origins and measurement methods of that data in detail here.) Looks like the temperature has been going up since 1880, when we started really systematically burning fossil fuels.
In the top graph (a), the yellow line is a model of what scientists calculate the temperature would have been accounting only for natural processes that might change it. Volcano eruptions, tiny changes in solar energy output and Earth’s orbit. Lots of data — measured aerosol particle counts from volcanic eruptions that have occurred, and so on — go into the calculation of the yellow line, which is done with a model (that model, itself, is informed by laboratory measurements of radiation scattering by aerosol particles, etc.) There’s a pretty big difference between the black line and the yellow line in recent years — looks like natural causes can’t explain our temperature data.
The middle graph (b) considers the modeled temperature effects of all the human activities that might influence global temperature. Again, lots of data (more below) goes into these calculations. The red line is the modeled expected temperature based on all the anthropogenic (human-induced) effects and neglecting all natural causes. Not perfect, but it fits the black measurement data from our thermometers much better then the yellow line in (a).
The bottom graph (c) considers all the natural and human-induced effects to make the orange calculated line. The orange line pretty much sits right on top of the black measurements.
Sarah: “modeling … is extremely hard to do when you’re talking about the climate.”
Well, she’s right. The model isn’t perfect, and that’s why there’s an orangey cloud around the orange line in (c). The cloud represents a scientific assessment of the uncertainty in the model.
The graph above is a summary of tons of data, much of which is laid out in some detail in Volume I of the administration’s climate report, released in 2017. For example:
All in all, the data points to these as the key drivers of the measured increase in global temperature since the Industrial Revolution:
Looks like the data says,
- the global temperature has been going up since the Industrial Revolution and not really before that; and
- it’s explainable mainly by emissions of greenhouse gases, and not at all explainable without accounting for greenhouse gases …
- with perhaps a teeny, weeny little bit of help from a natural increase in solar irradiance.
In fact, the claim at the top appears to be nothing if not “data driven!”
Sarah seems to doubt the veracity of the model — the orange line and uncertainty cloud in graph (c) — for making forecasts about the future. I mean, it’s not perfect. Maybe Sarah doesn’t like the way the black line squiggles down while the orange line squiggles up around the year 1910. Point taken.
But, assuming the quality of life of my children and grandchildren, and the future survival of human civilization on Earth, might well depend on decisions we make right now, the question is, is the orange model good enough to make those decisions?
Sarah “would like to see something that is more data driven.” Well, we could wait and go on with business as usual, as Sarah seems to suggest, until we just make more temperature measurements clear out to the year 2100 and beyond. Then, we would have all the data. Our conclusions about fossil fuel combustion and the climate would be precisely and perfectly “data driven!” No models required! Great idea!
(Oh, except by then we might be on an irreversible path to civilization collapse and human extinction. Oops.)
We’ll search the report for more data (assuming it’s in there) in the coming days…
#rescuethatfrog