The Definition of Science

It's astonishing the rhetorical and cognitive contortions climate change deniers and flat earthers will go through to keep living in their fantasy worlds. Climate science is incontrovertibly real science, which by rigorous and multiple lines of inquiry has reached conclusions as certain as any can be that humans, by spewing carbon dioxide and methane into the atmosphere, are causing overall warming of the troposphere and oceans. This in turn causes multiple changes in weather patterns including wetter and more powerful storms, more heat waves, droughts and associated wildfires, and severe ecological disruption, among other consequences.

It is true that climate science is at the highest, most integrative level, not experimental. There isn't a second earth where we aren't spewing greenhouse gases to which we can compare this one. But astronomy, cosmology, paleontology, and many other perfectly respectable sciences do not have much room for grand experiment either. However, experiments do provide much of the underlying scaffolding of knowledge for these observational sciences. For example, astronomy and cosmology depend on physics which is experimentally testable here on earth, and paleontologists also use physics and chemistry to test their observational and deductive methods.

There is a sort of junior high school mantra that people often chant to the effect that correlation can't prove causation, and a naive concept that only randomized controlled trials constitute "science." This is not true. Causation can be established by deduction from multiple facts and known relationships. In the case of climate science it's not even complicated, arcane or difficult. Svante Arrhenius in 1896 deduced the relationship between the CO2 content of the atmosphere and surface temperature. The mechanism is well understood and has indeed been confirmed my innumerable experiments. The atmosphere is largely transparent to visible light (which is why it's visible -- we evolved to be able to see wavelengths that penetrate the atmosphere). The ground and ocean are warmed by sunlight, and re-emit the energy in the infrared range, to which CO2 and methane are largely opaque. That's why an infrared photograph looks like it's taken in fog, and the range of visibility is low. The CO2 is in turn warmed by absorbing these photons and transfers its energy to the atmosphere and oceans with which it interacts. We know that this is why the earth is at a habitable temperature. We also know that as the CO2 (and methane) concentration in the atmosphere increases, so will the temperature.

This is not hypothesis, it is a fact as well known as any there is. We know that the seasons are caused by the inclination of the earth's axis of rotation to the plane of its orbit around the sun. We know that more CO2 in the atmosphere makes it warmer. Both of these facts are of equal stature. It is possible by various means to deduce the climate and CO2 concentration of the atmosphere in epochs both recent and long past. Global climate correlates with CO2 concentration in accordance with prediction. This is also true for the recent past for which we have direct, detailed records.

Scientists' observations of the atmosphere, with the benefit of satellites and global networks of sensors, have become more and more detailed. Combined with known physics and chemistry and yes, experiment, this enables them to relate atmospheric behavior with temperature, and to develop predictive models -- models which are then confirmed by events. There are obviously uncertainties in some predictions, but these are reduced as more observations and more detailed  models come into play.

I am very puzzled why people who have no training in a scientific subject think they know more than people who have devoted their lives to learning and research in the field. In any event, I hereby remind all readers of a policy which I announced some time ago and hereby reiterate:

Climate change denial is not permitted in comments here. We will not have a debate about it. There is no debate, there is no controversy, and I will not dignify willful ignorance with any further response.

Update: This post is about climate science, not the morality of abortion. I am generally disposed against comments that are radically off-topic or make category errors.