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Only statistical numbskulls would call it good news, but 2017 is set to be slightly less warm than the record-breaking 2016. Instead, it will merely be one of the three warmest years on record, and the hottest ever without an El Niño to boost temperatures. However, a massive programme of tree-planting could significantly reduce the warming trend.

The new temperature figures come from the latest State of the Climate report from the World Meteorological Organization.

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Climate negotiators are meeting in Bonn, Germany this week to discuss how to implement the pledges on curbing climate-warming greenhouse gases that were made in Paris in 2015. They have plenty to ponder. The WMO said the first nine months of this year were 1.1 °C warmer than pre-industrial levels. That means the world is more than two-thirds of the way to the limit of 1.5 °C agreed in Paris.

That is having real effects on real lives. Hong Kong and Shanghai, California and southern Spain have all experienced unprecedented temperature highs this year, the WMO reported. So, in the southern hemisphere, did Australia and Argentina. In May, temperatures reached a staggering 54 °C near the border between Pakistan and Iran, WMO Secretary-General Petteri Taalas said in Bonn. Around 30 per cent of the world’s population now lives in places where they suffer life-threatening heatwave conditions for several days a year.

At its winter maximum in March, the Arctic had less sea ice this year than ever recorded – matching the even greater recent declines in summer minima. But at least heavy snowfall added bulk to the Greenland ice sheet. In more bad news, the seas are rising faster again – at 3.5 millimetres a year.

Trees could help save us

Even the good news looks bad, said Chris Rapley of University College London, UK. “Whilst it is encouraging that human carbon emissions have levelled off over the last three years, the fact that 2016 still witnessed a record surge in atmospheric CO2 concentrations is ominous.”

In the run-up to the Bonn conference, climate scientists again said it was necessary to remove carbon dioxide from the air, by creating so-called negative emissions, as well as cutting our emissions.

Replanting forests could play a big role, the Woods Hole Research Center in Falmouth, Massachusetts announced last week. 100 billion tonnes of carbon – equivalent to roughly ten years of fossil fuel emissions – could be stored in forests. To do so, we would need to end deforestation and encourage the regrowth of 500 million hectares of forests that have been degraded by piecemeal logging.

Such an effort would be a one-off addition to nature’s carbon store. Once the trees were mature, they would stop absorbing more carbon dioxide. We would still need to cut emissions to zero by mid-century. Nevertheless, the plan “could help get the world at least a quarter of the way to limiting warming to 1.5 °C,” according to Woods Hole director Philip Duffy.

More on these topics:

New Scientist – Earth