Climate Change and the Course of Global History

By Bryan Walker 03/06/2014


The title in the Kindle Store was irresistible: Climate Change and the Course of Global History: A Rough Journey. American historian John L Brooke is the author, and the book is notable for its attempt to integrate climate science with the study of human history. In his acknowledgements the author brackets climate scientists with historians and archaeologists in the long list of people with whom he has corresponded and from whom he has received data and an understanding of scientific culture.

The scope of the book is as wide as human emergence in the evolutionary process, and before. It’s not my purpose to track through the long story the author has to tell or to follow the intricacies of the climate shifts he refers to. The book demands and rewards patient reading in these respects. But I offer a few comments arising from my reading of the book.

An historian making the effort to understand climate science as thoroughly as Brooke does seems to me in itself worth remarking. Often I could have been reading one of the many books by scientists or science writers that I’ve reviewed over past years on Hot Topic. The culture gap between the sciences and the humanities that C P Snow’s famous 1959 lecture lamented was certainly not evident in Brooke’s history. Five years ago I reported the plea of biographer Richard Holmes at the Hay Festival that we reject the notion of two cultures and accept the duty to understand the scientific discoveries of the modern age, a duty of crucial importance in the face of global warming. Brooke has clearly accepted that duty, though I fear many educated in the humanities continue to excuse themselves from it.

We are accustomed to think of the climate of the period since the end of the last ice age nearly twelve thousand years ago as relatively settled and favourable to the growth of human civilisation. But science reveals many variations within that comparatively civilisation-friendly climate environment, and Brooke explores the part those variations may have played in driving the significant developments and setbacks in the progress of civilisation.  Thus, for example, he considers the rise of the city and the early state can be partly understood as triggered by climate-related natural catastrophes: droughts in Egypt and Mesopotamia , floods in China and Peru, that led to population collapse and cultural crisis. “People died in huge numbers, villages were emptied, local gods discredited, ancient memories lost.” Out of this destruction rose the first states.

On the decline of the Roman period and the transition to the so-called Dark Ages Brooke points to the likelihood that a shift towards intense seasonal rains in the Mediterranean after centuries of moderately dry climate played a significant part in that decline.

The influence of climate in human history is often intertwined with other impacts, particularly epidemics and the human capacity for warfare. Brooke refers to them as a triad at the centre of any explanation of the long-extended collapse of the Roman Empire.

The book makes much of the distinction between exogenous and endogenous factors in the challenges historically faced by human societies. Climate reversals and epidemics are exogenous and need to be given due weight. Brooke comments in this regard that “the new climate science has destroyed the refuge of sceptical historians, who traditionally discount the impact of natural forces because they presumably operated as an unknowable constant”.

Those impacts are, he observes, now both knowable and revealed as not constant. In that observation lie a host of possible improved understandings of the human past.

As Brooke follows the historical picture into modern times he acknowledges the arrival of the Anthropocene. The enormous explosion of human population is serviced by an energy structure which is now literally transforming the earth system.

This presumably implies that climate change is no longer an exogenous factor. It is our choices within society which determine what it will bring. Given his climate change perspective it is natural that Brooke looks ahead to a global struggle in the decades to come. He notes that some already claim that the wider impact of climate change is the vehicle of genocide by the north being perpetrated against the global south. Harsh words, perhaps, but in view of the effects on human society of the climate variations of the Holocene it is unlikely that the much larger changes caused by anthropogenic global warming will have less than drastic effects on humanity. The rough journey of the book’s subtitle may well turn catastrophic in our heavily populated world.

But the issue is now one within our power to deal with. Brooke’s penultimate sentence: ”We hold it in our collective capacity to address the earth system crisis that is now upon us.” And finally the crunch: “That capacity must be mobilized by an informed political will.”

That informed political will seems a long way off. The same day that I wrote this I heard our own climate change minister Tim Groser indignantly expostulating on the radio news in response to the Green Party’s carbon tax policy as if they were set upon the destruction of New Zealand’s economy. It didn’t help that he instanced the Australian government’s determination to abandon their carbon tax as evidence of how unthinkable the Green’s policy is. The political will of the climate change minister seems more directed towards defending entrenched economic interests than to the issue for which he is nominally responsible.

On the other hand, the same day saw President Obama initiate what at long last seems to be a genuine move to major emissions reduction in the US. Brooke identifies angry pessimism and concerned pragmatism as broad alternatives for those who take climate change as seriously as it deserves. He clearly still has hope that pragmatism can win through against the powerful forces of denial. I imagine he will be taking more pleasure in his President’s move than I in the stolid indifference of the NZ government.