Human influence on Hurricane Harvey far larger than previously thought
New Zealand-led research has found the climate change damages from a single hurricane in the US are more than three times those estimated for the whole country over an entire year. The researchers have created a method to separate the damages caused by the 'normal weather' of a storm, from the damage due to human-induced climate change. They say it means the conventional models are substantially underestimating the current costs of climate change.
Hurricane Harvey was just one of four major hurricanes to make landfall in the US in 2017; it caused 107 deaths and was one of the most economically damaging tropical storms in recorded history. New research estimates the damages of Harvey that are linked to human-caused climate change are as much as $67 billion dollars.
The research, led by scientists and economists from New Zealand and California, develops a new way of combining climate science with the economics of natural disasters.
“It is only fairly recently that scientists have been able to quantify how much of a storm or drought or heatwave is ‘normal weather’ and how much is due to human-induced climate change. This is the science of ‘event attribution’,” says the study's lead author, Professor Dave Frame of Victoria University of Wellington.
"We combine this kind of event attribution science with estimates of the damages associated with Hurricane Harvey," says Prof Frame. "The method we have developed combines economic data about the costs of disasters with information about how the odds of an event like extreme rainfall or a drought are changing as the climate changes."
A recent study by the US EPA estimated perhaps 10% of global climate change costs occur in the US; and the economic models on which the social cost of carbon is based suggest global costs in the vicinity of US$210 billion at 1°C above pre-industrial levels. Putting these together, the current expected costs of climate change for the whole USA ought to be somewhere around $21 billion for a whole year; much less than the US$67 billion from the single event found in the new study.
"The research shows there is a very sharp contrast between our attribution-based approach and that which emerges from conventional economic models of climate change.” said Professor Ilan Noy of Victoria University of Wellington.
“We are pretty sure the conventional models – Integrated Assessment Models, or IAMs – very substantially underestimate the current costs of climate change.”
Noy continues “The IAMs consider only some costs of global warming without adequately taking account of the costs of extreme weather events, which are the means through which most damage is done, and which climate change is making more common. So, the estimates are much too low because they are very insensitive to extreme weather events.”
"We think this research will be of particular value to organisations like central banks, treasuries and financial organisations and investors who care about changing climate change risks," said Dr Michael Wehner of Lawrence Berkeley National Laboratory.
The new work builds on fifteen years of event attribution studies aimed at quantifying human influence on damaging extreme events. Professor Myles Allen of the University of Oxford first proposed in 2003 that if human influence on extreme weather could be quantified, it could be used to hold emitters responsible for damages arising.
Professor Allen says, “This research is the logical culmination of the science of event attribution, and confirms that the total cost of human influence on climate already far exceeds estimates of the net cost from traditional integrated assessment models.”
“Event attribution is a young and rapidly growing branch of climate science," says Dr Suzanne Rosier of NIWA. "The results are indicative rather than definitive but as the field matures we will be able to quantify the economic and social effects of extreme events, and the human fingerprint on extreme events. That will allow us to develop a much more complete picture of the costs attributable to climate change.”
Frame said the research he and his colleagues were conducting had the aim of “helping decision-makers have a broader, deeper and more accurate understanding of the effects of climate change on the economy”.
The research paper: “The economic costs of Hurricane Harvey attributable to climate change” by Dave Frame, Michael Wehner, Ilan Noy and Suzanne Rosier is published at Climatic Change.