Paris, France | AFP
Frustrated with inaction on catastrophic global warming, citizens are hauling governments and big polluters before the courts calling for "climate justice".
Increasingly the cases invoke human rights, particularly the right to life.
The Sabin Center for Climate Change Law at Columbia University has counted more than 1,700 legal cases filed across the globe, with over 1,300 in the United States.
"We've seen over the last five years a dramatic increase in the number of cases filed in the US and all over the world," the Sabin Center's executive director Michael Burger told AFP.
The rapid growth in legal cases reflects society's frustration with the extent of climate inaction, he said.
While many cases are in richer countries, there are around 40 cases in developing nations, according to the British Grantham Research Institute on Climate Change. And the number is rising.
Courts do not necessarily rule in favour of those seeking to defend the environment.
"Litigation is the last resort and a risky proposition at best," said Burger.
"There are going to be wins and losses."
In the US, the Oregon court of appeal in January rejected a lawsuit filed by children in 2015 that sought to force the American government to protect public resources from climate change.
"Very few lawsuits have really succeeded in producing positive results for the moment," researcher at France's Pantheon-Sorbonne university Marta Torre-Schaub told AFP.
But she added that states and companies take these issues seriously "because they know there is a risk of litigation".
In a landmark case last year the Dutch Supreme Court ordered the state to slash its greenhouse gas emissions by at least 25 percent of 1990 levels by the end of 2020.
Similar cases are in the works. In France campaigners backed by over 2 million citizens are seeking to hold the government to account for "climate inaction" in a so-called "Case of the Century".
Fossil fuel companies responsible for huge CO2 emissions are in the firing line. Claimants are seeking not only compensation but also a change in practices.
A German court ruled in November 2017 that it would hear a Peruvian farmer's case against energy giant RWE over climate change damage in the Andes.
NGOs have deposited lawsuits in France against oil giant Total for not doing enough to reduce its carbon emissions.
And this month environmental groups faced Shell before a Dutch court to force the oil giant to meet emissions targets in the Paris climate accord.
Some lawsuits specifically aim to pull the plug on projects.
Last year, Australian courts refused to grant permission for a new Rocky Hill open-cut coal mine, citing the proposed mine's contribution to climate change.
Britain's appeals court in February ruled in favour of environmental campaigners who oppose the building of a third runway at London's Heathrow airport. The airport is taking the case to the supreme court.
Activists facing trial for civil disobedience actions taking aim at big polluting companies often invoke the "climate emergency". Some judges have been receptive to these arguments.
Switzerland's appeals court in October acquitted a protester who smeared red paint on a Credit Suisse bank, targeted because of its financing of fossil fuels.
But in September a different Swiss appeals court convicted activists who invaded a Credit Suisse branch dressed as Roger Federer to denounce the tennis star's sponsorship deals with Switzerland's biggest bank.
In France, some demonstrators who unhooked and pocketed portraits of President Emmanuel Macron hanging in town halls to protest the "void in government (climate) policy" were discharged, but others were convicted.
Attributing cause and effect on a planetary scale is a tricky question in environmental lawsuits.
"Holding any one actor responsible for any one particular event raises issues of causation and responsibility," Columbia University's Burger told AFP.
But the science of attribution is becoming ever more sophisticated.
Researchers concluded this summer's heatwave that engulfed Russian Siberia would have been "almost impossible" without climate change.
Numerous scientific studies have also succeeded in breaking down the main CO2 emissions, by company or by country.
The Climate Accountability Institute, which tracks the CO2 and methane emissions of the biggest polluters, said in December 2019 that the 20 worst offenders have produced 35 percent of all fossil fuel emissions since 1965.
In recent years jurisdictions have attributed rights to natural features such as rivers, mostly in Asia and Latin America.
The Colombian Atrato River was recognised as a legal entity with rights by the constitutional court in 2016. The supreme court granted the same status to the Colombian Amazon in 2018.
"It's very important that the natural world is accorded legal status," said Jojo Mehta, chair of the Stop Ecocide Foundation.
"But these rights can be trodden on if there is no punishment for treading on them. Unless you have a crime of murder your right to life is not really well protected."
Paris, France | AFP