Countries and individual companies could end up being sued for their contribution to climate change, suggest scientists who have quantified how global warming increases the risk of freak weather events.
Myles Allen and colleagues tested their technique for measuring risk on the European heat wave of 2003 which killed thousands of people. They found that emission of greenhouse gases has at least doubled and more likely quadrupled the risk of such a severe event happening.
“The fraction of risk due to human events is starting to reach the level where a court might find the emitters responsible,” says Allen, at the University of Oxford, UK. This means, for example, that relatives of those who died during the heat wave could consider seeking compensation.
Already, US states have filed a lawsuit against power companies for failing to control carbon dioxide emissions. “Litigation in relation to greenhouse gases is increasingly likely,” writes Allen in his Nature article, co-authored by Richard Lord, a QC (senior attorney) from Brick Court Chambers in London, UK.
To calculate how much humans were to blame for the 2003’s heat wave, the team used computer simulations developed by the UK’s Met Office. They compared the frequency of heat waves in today’s greenhouse-gas polluted world to their frequency in the simulated, uncontaminated environment.
The results from many runs of the climate model suggest that extreme heat waves can now be expected once every 250 years but would have happened less than once in 1000 years if there were no extra greenhouse gases in the atmosphere.
While severe heat waves are still extremely rare, the chances of them happening are increased, explains Allen. “We have loaded the weather dice.”
Increasing the odds of an adverse event can be enough to make an entity liable for damages - as seen with tobacco companies. Class-action lawsuits against them have been underpinned by scientific evidence that smoking increases the risk of developing lung cancer.
It is not possible to link any individual case of the disease to smoking because there are other causes too. Similarly, no particular climate event can be blamed on global warming, but now Allen and colleagues have shown they can calculate a change in risk.
The only difference, says Allen, is that the risk attached to smoking was calculated by comparing the fate of large numbers of people, some smokers, some not. The same statistical techniques cannot be applied directly to the climate because the Earth has only one. They have to use simulated models to generate comparisons.
“A crucial thing for the courts to decide will be whether this kind of evidence is admissible,” Allen told New Scientist. If it is, courts will then have to deal with the more complex question of who to hold responsible.
Journal reference: Nature (vol 432, p 551, p 610)