Apollo astronauts being well known for their expertise in climate science.
To be fair, most people who lecture me on climate change aren't exactly experts in the field either.
But they have the acceptable conclusions, which proves that they know what they are talking about I guess.
My thought on the matter is that pretty much no one knows the first thing about the climate. The weather system of the earth is infamously one of the most complex things that we try to analyze, and to make predictions over a long term is incredible difficult. Not necessarily impossible, but also not something which can be boiled down to a simple argument. So unfortunately this field is really only available to those people willing to put a long time in studying physics, meteorology, dynamical systems, partial differential equations, computer modeling, etc. Every successful model requires each of those fields in nontrivial ways, which makes it difficult for a layman (even one with some experience in one of those fields) to follow the results.
The best that we can hope to do is to keep track of what the current predictions are and see if they come true.
97% of published peer-reviewed scientific papers that took any kind of a stance on climate change has stated that it is occurring and it is man made. Once people like this astronaut start publishing peer-reviewed papers that show his findings, methods of finding the data, and drawing proper conclusions from them, I will pay attention to him.
If your response is some kind of conspiracy theory in the scientific community, save your breath.
I am a mathematician and I have seen colleagues take stances in their papers about climate change, even though their research is at best tangentially related to it. Why do they do it? Because climate change is a hot item now and it is easy to get funding if you mention it.
If you know anything about academia you will know that research is determined primarily by funding. You will also know that "peer review" is sadly not always a measure of quality control due to certain journals which practice a sort of quid pro quo, if I let your paper slip through then you'll let my paper slip through, sort of arrangement. It's a consequence of the number of departments that require X number of papers per year for tenure or advancement without worrying so much about the quality of the papers (especially since these decisions are often made by a dean or provost who doesn't necessarily know anything about the subject, eg. a Dean of Science who is actually a Chemist reviewing the work of a Psychologist, and thus cannot judge the quality himself).
This makes it very easy for trends to occur and stick around. In fact, I think at this point there are probably more mathematicians than physicists writing about String Theory, simply because it became an easy way for mathematicians to get funding.
