Leading economists called Monday on the international community to price carbon at up to $100 (89 euros) a tonne by 2030, saying this was "indispensable" in the fight to slash emissions.

"A strong and predictable carbon-price trajectory provides a powerful signal to individuals and firms that the future is low carbon, inducing the changes needed in global investment, production and consumption patterns," said the commission of leading economists headed by Joseph Stiglitz and Nicholas Stern.

Countries should set a target of reaching $40 to $80 per tonne of CO2 by 2020, and of $50 to $100 per tonne by 2030, they said.

The idea is that the cost will force companies and individuals to turn to more climate friendly options, while at the same time raising funds for states to invest in cleaner infrastructure.

"The revenue can build up to something substantial," noted Stern.

Carbon trading mechanisms are in place in a handful of countries and in the European Union.

The EU fixes emissions reduction obligations and allows companies or countries to trade quotas, buying or selling depending on whether they have surpassed or remain inside set limits.

Canada has also announced a minimum price of Can$10 (US$7.63) per tonne of carbon pollution in 2018 and China, after provincial experiments, is set to launch a national market next year.

But the implementation of the landmark 2015 Paris deal to curb global warming has hit a major roadblock as US President Donald Trump said he would only decide this week whether the US would abide by the deal.

Nevertheless, as Stiglitz noted: "The global community has to recognise that it is a global problem."

Cities may be 8 degrees Celsius hotter by 2100: study
Paris (AFP) May 29, 2017 - Under a dual onslaught of global warming and localised, urban heating, some of the world's cities may be as much as eight degrees Celsius (14.4 degrees Fahrenheit) warmer by 2100, researchers warned Monday.

Such a temperature spike can have dire consequences for the health of city-dwellers, robbing companies and industries of able workers, and put pressure on already strained natural resources such as water.

The projection is based on the worst-case-scenario assumption that emissions of planet-warming greenhouse gases continue to rise throughout the 21st century.

The top quarter of most populated cities, in this scenario, could see the mercury rise 7 C or more by century's end, said a study in the journal Nature Climate Change.

For some, nearly 5 C of the total would be attributed to average global warming.

The rest would be due to the so-called Urban Heat Island (UHI) effect, which occurs when cooling parks, dams and lakes are replaced by heat-conducting concrete and asphalt -- making cities warmer than their surrounds, the researcher said.

"The top five percent (of cities per population) could see increases in temperatures of about 8 C and larger," study co-author Francisco Estrada of the Institute for Environmental Studies in the Netherlands told AFP.

Estrada and a team used different projections of average planetary warming, combined with the UHI effect and potential harms, to estimate the future costs of warming on cities.

The median city, right in the middle of the range, stands to lose between 1.4 and 1.7 percent of GDP per year by 2050 and between 2.3 and 5.6 percent by 2100, they concluded.

"For the worst-off city, losses could reach up to 10.9 percent of GDP by 2100," wrote the team.

UHI "significantly" increases city temperatures and economic losses from global warming, they added.

This meant that local actions to reduce UHI -- such as planting more trees or cooling roofs and pavements, can make a big difference in limiting warming and minimising costs.

Cities cover only about one percent of earth's surface but produce about 80 percent of gross world product and account for around 78 percent of energy consumed worldwide, said the researchers.

They produce more than 60 percent of global carbon dioxide emissions from burning coal, oil and gas for fuel.

The world's nations agreed in Paris in 2015 to the goal of limiting average global warming to two degrees Celsius over pre-Industrial revolution levels by curbing greenhouse gas levels in Earth's atmosphere.

For the latest study, researchers used data from the world's 1,692 largest cities for the period 1950 to 2015.

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Paris climate commitment 'crippling' to US growth: White House
Taormina, Italy (AFP) May 26, 2017
US compliance with its commitments under the Paris Agreement on climate change would be "crippling" to growth, the White House said Friday. During his election campaign, avowed climate sceptic Donald Trump promised to exit the 2015 UN pact on limiting global warming. But Trump has now said he will make a decision after returning to Washington following the G7 summit in Sicily which start ... read more

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