This is a very good point. But, sadly, there is a counter-argument.
With something like celestial mechanics the underlying principles are relatively simple - Newtonian mechanics has been completely understood for centuries and experimentally verified countless times. On a short timescale (hundreds/thousands of years) the many-body corrections to the basic three-body (sun, moon, earth) calculation are negligible. Off the top of my head I think the relativistic corrections are negligible too, but even if they aren’t we know how to do those sums and again they have been verified time after time after time. The degree of doubt in these calculations is essentially zero. And the observations are not open to multiple explanations. A planet either arrives where and when the calculations say it should or it doesn’t. Wrong theories can be eliminated quickly and ruthlessly because they give verifiably wrong answers.
Climate change and a lot of the life-science stuff, on the other hand, are enormously complex and contain elements which are verging on the chaotically unstable. Here is an overview of climate science http://images.slideplayer.com/12/3377551/slides/slide_1.jpg. Each one of the short phrases on the diagram has a chunk of science behind it which is keeping hundreds of experts busy full-time. It’s a miracle that we can actually draw any worthwhile conclusions from it having only studied it for a few decades. When it comes to the life-sciences here is the basic metabolic pathways diagram. You may need to blow this up in size. A lot. https://www.cc.gatech.edu/~turk/bio_sim/articles/metabolic_pathways.png. Again the complexity is almost mind-boggling and outcomes from these processes can depend very sensitively on numbers which we still can’t measure accurately.
Scientists working in these complex, mathematically sensitive areas have to be realistic and to try to put confidence levels on their predictions (e.g. I am 70% sure that my prediction is within +/-5% of what will happen, and I am 98% sure that my prediction is within +/-25% of what will happen). As long as there is some possibility, however small, that the predictions could be wrong though, there will be people (usually with a vested interest) who will say that the scientists “can’t be absolutely sure”. Then the question becomes “How sure do the scientists have to be before we accept that we need to change something just in case they are right ?”.
Then you pays your money and you takes your choice.