Steven Koonin has written an article in the Wall Street Journal called Climate Science Is Not Settled. According to his bio at the end,

Dr. Koonin was undersecretary for science in the Energy Department during President Barack Obama’s first term and is currently director of the Center for Urban Science and Progress at New York University. His previous positions include professor of theoretical physics and provost at Caltech, as well as chief scientist of BP, where his work focused on renewable and low-carbon energy technologies.

If I can paraphrase and oversimplify, he thinks that climate science is still too uncertain to make any decisions other than investments in “low-emissions technologies and in cost-effective energy-efficiency measures.” And lots more research, of course. Here is a short passage:

Even though human influences could have serious consequences for the climate, they are physically small in relation to the climate system as a whole. For example, human additions to carbon dioxide in the atmosphere by the middle of the 21st century are expected to directly shift the atmosphere’s natural greenhouse effect by only 1% to 2%. Since the climate system is highly variable on its own, that smallness sets a very high bar for confidently projecting the consequences of human influences.

A second challenge to “knowing” future climate is today’s poor understanding of the oceans. The oceans, which change over decades and centuries, hold most of the climate’s heat and strongly influence the atmosphere. Unfortunately, precise, comprehensive observations of the oceans are available only for the past few decades; the reliable record is still far too short to adequately understand how the oceans will change and how that will affect climate.

A third fundamental challenge arises from feedbacks that can dramatically amplify or mute the climate’s response to human and natural influences. One important feedback, which is thought to approximately double the direct heating effect of carbon dioxide, involves water vapor, clouds and temperature.

But feedbacks are uncertain. They depend on the details of processes such as evaporation and the flow of radiation through clouds. They cannot be determined confidently from the basic laws of physics and chemistry, so they must be verified by precise, detailed observations that are, in many cases, not yet available.

You don’t want legitimate scientists with alternative viewpoints to be censored or silenced, so it’s good to read through something like this and draw your own conclusions, while keeping in mind an overwhelming majority of scientists have come to the conclusion that the science is certain enough, and the potential consequences serious enough, to justify action now. His last argument makes no sense to the engineer in me at all, that we shouldn’t try to make projections now using our best understanding of the physical relationships in the system, that we just have to wait until there are changes large enough that we can measure them. If we always did that the entire fields of science, engineering and technology would pretty much grind to a halt, and the rest of our civilization with them.