In 2011, climate scientist Kevin Trenberth wrote one of the most important scientific papers on climate change in history. Its lessons remain unlearned.
In “Attribution of climate variations and trends to human influences and natural variability,” published in WIREs Climate Change in 2011, NCAR climatologist Kevin Trenberth shattered the lie implicit in almost all scientific communication, policymaking, and journalistic coverage of climate change and its causal relationship with extreme weather.
As the abstract explains in scientific terms:
Past attribution studies of climate change have assumed a null hypothesis of no role of human activities. The challenge, then, is to prove that there is an anthropogenic component. I argue that because global warming is ‘‘unequivocal’’ and ‘very likely’ caused by human activities, the reverse should now be the case. The task, then, could be to prove there is no anthropogenic component to a particular observed change in climate, although a more useful task is to determine what it is. In Bayesian statistics, this change might be thought of as adding a ‘prior’. The benefit of doubt and uncertainties about observations and models are then switched. Moreover, the science community is much too conservative on this issue and too many authors make what are called ‘Type II errors’ whereby they erroneously accept the null hypothesis. Global warming is contributing to a changing incidence of extreme weather because the environment in which all storms form has changed from human activities.
Trenberth’s article precisely described the phenomenon identified in climate science communication at the time by writers like myself. In a 2010 article entitled “If Doctors Were Climate Scientists, We’d Be Dead,” I listed several examples of climate journalism and quotations from climate scientists privileging the false null hypothesis:
“it is impossible to blame mankind for single severe weather events”
“language — which suggests that we can, in fact, attribute specific weather events to global warming — should be strictly avoided”
“the usual caveat that no current weather event can be said to be ‘caused’ by climate change”
“As we continually stress, one extreme weather event, or even a series of weather events, is not caused by global warming or climate change”
“you cannot say a single event or a single summer is unequivocally due to climate change — by definition it’s weather, and not climate”
“a single weather event cannot be blamed on climate change”
“climate change cannot be said to cause an individual event”
“You can’t attribute any single weather-related event to a hotter planet”
This seeding of false doubt continues to this day, to the benefit of no one but the polluters profiting from our inaction.
“The result of bad and misleading statements about attribution, of which there have been many, is to grossly underestimate the role of humans in climate events of note in recent times to the detriment of perceptions about climate change and subsequent policy debates,” Trenberth wrote in 2011. “Humans are changing our climate. There is no doubt whatsoever.”
We have exactly one planet to live on, and it’s one whose climate system is now being driven by manmade pollution. The coming changes which are known with absolute certainty — sea level rise, glacial decline, ocean acidification — presage suffering on an apocalyptic scale. There is no alternate planet with everything the same except with pre-industrial levels of carbon dioxide to compare against. Weather phenomena are determined through physical processes by the state of the ocean-atmosphere system, making greenhouse pollution one of the causative agents of today’s weather.