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Greenhouse gas emissions from major world cities ‘have already peaked’, say leaders

Image credit: DT

The greenhouse gas emissions from 27 major cities around the world have peaked despite growing populations and economies, according to a body representing city authorities.

The list of cities includes major hubs like New York and London and C40 Cities said it marks a major milestone in achieving the aims set forth in the Paris Agreement.

C40 is a network of over 90 of the world’s megacities committed to addressing climate change. It was formed from a joint agreement between major metropolises around the world in 2006 as part of a collaborative project between former President Bill Clinton and ex-London Mayor Ken Livingstone.

The body said that cities had reduced their emissions by cutting their usage of fossil-fuel-generated energy, growing their public transport systems and reducing waste.

In order to avoid the worst impacts of climate change it has predicted that developed cities around the globe will need to have peaked their emissions by 2020 at the latest.

Meanwhile, major cities in developing nations may continue to grow their overall output until between 2030 and 2035 before they too must peak.

Paris’ Mayor Anne Hidalgo said it was a relief to “finally share good news on climate change.”

With economies continuing to grow even as emissions stagnate or fall, “we can prove that we can also create jobs, create opportunities with the ecological transition,” she told reporters.

Global warming is currently set to exceed the more ambitious limit of 1.5 degrees Celsius called for in the 2015 Paris Agreement to curb climate change, according to a draft UN report due for publication in October.

Under President Donald Trump, the United States - the world’s second largest greenhouse gas emitter - has weakened the Paris pact by announcing last year it intended to pull out of the deal.

Determining when a city has peaked is not always straightforward, C40 said. While emissions may plateau or decline for a few years, it is no guarantee that this will not reverse in the future.

To provide sufficient confidence that a peak reflects a definitive maximum of emissions, the body says it takes a conservative approach and only considers a city as having peaked in the past if it meets the following three principal criteria:

  • The emissions reached a maximum level at least 5 years before the most recently recorded year. If the peak is very recent, a change in emissions could potentially be due to short-term fluctuations caused by extreme weather or an economic downturn rather than indicative of a longer-term trend of reducing emissions.
  • The emissions at peak level are at least 10 per cent higher than the most recent inventory year. Again, this is to eliminate “false” peaks due to short-term fluctuations. When looking at the average annual reduction rate in emissions in cities that have peaked, the mean value is 2 per cent, which is equivalent to a 10 per cent reduction over a five-year period.   
  • The city has made a public commitment to deliver further emission reductions.

The absence of developing world cities from the list suggests they may need more funding to make needed changes, Hidalgo said.

“We must strive toward funds going toward the ecological and energy transition where it is most urgent, including in developing cities,” she said.

Michael Burger, executive director of the Sabin Center for Climate Change Law at New York’s Columbia University, said it was expected that poorer countries, many of them still growing, might still see emissions increases.

“It is a fact that countries are on different development pathways and so different cities are going to peak emissions ... at different times,” he said.

In June C40 raised concerns in a report that 1.25 million people living in London and £200bn worth of assets in the UK capital may be severely impacted by climate change by the year 2050. 

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