I read Freeman Dyson’s review of A Question of Balance: Weighing the Options on Global Warming Policies, by William Nordhaus, earlier this week. Afterwards, I started wondering about the historical, or rather pre-historical, levels of atmospheric carbon dioxide. This morning I saw, on Jerry Pournelle’s journal, a link to a sourced article, The Past and Future of Climate, by David Archibald, which presents data related to that very question.

All of this really means we need more research before we race to go Do Something. That is, we should have a much better understanding on what exactly is happening and what human measures will have, if any, before enacting costly change.

For example, reading the two articles makes me ask, if an increase in atmospheric CO2 increases plant growth, and seasonal plant growth measurably decreases CO2 levels, what impact will increase growth rates have on global CO2 levels? If the answer is obvious, then think about the possible variables. I do not see any certainty. For example, if the earth is still warming or even cooling, from, say, a change in solar activity, how will this affect growing season length and carbon uptake? Will a cooling period be buffered by increase plant growth, despite shorter seasons? What is the possible economic impact?

The science is not settled. Nullius in Verba indeed.