Thu, Aug 11, 2016 page9

• Upper limit for global warming close to being broken

  Scientists are warning that global warming is already close to breaking though an upper limit of 1.5oC, a key target that was set at the Paris climate negotiations in December last year

  • By Robin McKie / The Observer
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  Leading climate scientists have warned that the Earth is perilously close to breaking through a 1.5°C upper limit for global warming, only eight months after the target was set.

  The decision to try to limit warming to 1.5°C, measured in relation to pre-industrial temperatures, was the headline outcome of the Paris climate negotiations in December last year.

  The talks were hailed as a major success by scientists and campaigners who said that, by setting the target, desertification, heat waves, flooding and other impacts could be avoided.

  

  Illustration: Mountain people

  However, figures — based on the UK’s Met Office data — prepared by meteorologist Ed Hawkins of Reading University, show average global temperatures were already more than 1°C above pre-industrial levels for every month except one over the past year and peaked at +1.38° C in February and March.

  Keeping within the 1.5°C limit will be extremely difficult, scientists say, given these rises.

  These alarming figures will form the backdrop to the Intergovernmental Panel on Climate Change (IPCC) talks in Geneva this month, when scientists will start to outline ways to implement the climate goals set in Paris. Dates for abandoning all coal-burning power stations and halting the use of combustion engines across the globe are likely to be set.

  Atmospheric heating has been partly triggered by a major El Nino event in the Pacific, with this year expected to be the hottest year on record. Temperatures above 50°C have afflicted Iraq; India is experiencing one of the most intense monsoons on record; and drought-stricken California has been ravaged by wildfires.

  Stanford University professor Chris Field, co-chair of the IPCC working group on adaptation to climate change, told the Observer: “I would say the 1.5°C goal now looks impossible or at the very least, a very, very difficult task.”

  The Paris summit first agreed to limit global warming to 2°C above pre-industrial levels and then decided to try to keep it below 1.5°C. This latter limit was set because it offered the planet a better chance of staving off catastrophes such as the melting of polar ice, which would no longer be able to deflect solar radiation and allow even greater global warming.

  “If the world puts all its resources into finding ways to generate power without burning fossil fuels, and if there were international agreements that action must happen instantly, and if carbon emissions were brought down to zero before 2050, then a rise of no more than 1.5°C might just be achieved,” said Ben Sanderson of the US National Center for Atmospheric Research in Boulder, Colorado.

  “That is a tall order, however,” he said.

  The problem was made particularly severe because moving too quickly to cut emissions could also be harmful, Field added.

  “If we shut down fossil fuel plants tomorrow — before we have established renewable alternatives — we can limit emissions and global warming, but people would suffer. There would be insufficient power for the planet,” he said.

  The Paris agreement is vague about the exact rate at which the world’s carbon emissions should be curtailed if we are to achieve its 1.5°C target. It merely indicates they should reach zero by the second half of the 21st century, a goal that was accepted as being ambitious, but possible — until global temperatures increased dramatically this year.

  “It means that by 2025, we will have to have closed down all coal-fired power stations,” Potsdam Institute for Climate Impact Research director John Schellnhuber said.

  “And by 2030, you will have to get rid of the combustion engine entirely. That decarbonization will not guarantee a rise of no more than 1.5°C, but it will give us a chance,” he said.

  Many scientists believe the most realistic strategy is to overshoot the 1.5°C target by as little as possible and then, once carbon emissions have been brought to zero, carbon dioxide could be extracted from the atmosphere to cool the planet to 1.5°C.

  In other words, humanity will have to move from merely curtailing emissions to actively extracting carbon dioxide from the air, known as negative emissions.

  “Some negative emission technology will have to be part of the picture if you are going to keep 1.5C as your limit,” said Jim Skea, a member of the UK government’s Committee on Climate Change.

  “There will always be some activities that put carbon into the atmosphere and they will have to be compensated for by negative emission technology,” he said.

  What form that technology takes is still unclear. Several techniques have been proposed, but most are considered unworkable — with the exception of bioenergy with carbon capture and storage. Under this scheme, vast plantations of trees and bushes would be created, their wood burned for energy while the carbon dioxide emitted was liquefied and stored underground.

  “It could do the trick,” Cambridge University climate expert Peter Wadhams said. “The trouble is that you would need to cover so much land with plants for combustion you would not have enough space to grow food or provide homes for wildlife. We just have to hope that some kind of extraction technology is developed in the next couple of decades. If not, we are in real trouble.”
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