Obligations in COP26 | Warming forecasts may be overly optimistic

(Paris) A study published Monday confirms that warming projections made by the United Nations based on commitments and policies to reduce greenhouse gas emissions are more uncertain than one might think.

According to the latest UN estimates, despite the new commitments for 2030 announced before and during the COP26 climate conference, the world is still heading towards a “catastrophic” 2.7°C warming by the end of the century. than the Paris Agreement to limit it much to +2°C, if possible +1.5°C, compared to the pre-industrial era.

But the apparent accuracy of these predictions is misleading, according to the study published Monday in the journal The nature of climate changeSeveral of its authors also participated in the development of the UN assessment, in which they are skeptical.

Because of the “misleading accuracy” of announcements made during COP26 in Glasgow, “countries may think they are making progress when the opposite is true,” commented lead author Ida Sognnaes, of the CICERO Research Center in Oslo.

Most climate projections rely on models that start from a desired final temperature of 2100 – +1.5 °C or +2 °C for example – and work backwards to determine the levers needed to achieve this, by adjusting variables such as the use of coal or the development of renewable energy sources. .

But “our study is ‘expectations’,” insists Glenn Peters, also a researcher at CICERO. “We represent where current policies are taking us and we look at where we are.”

Seven climate modeling groups used this method to assess commitments made for 2030 by the 200 or so countries that signed the Paris Agreement. The result, estimates range from +2.2°C to +2.9°C.

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But if the numbers themselves are not far from those of the United Nations, researchers point to its lack of certainty.

If we look at the lower end of the range, it may indicate that we are really close to the goals of the Paris Agreement. […] But warming is likely to be around 3°C, which would require much stronger policies.

Glenn Peters, Researcher at CICERO

Most studies of the effects of global warming compare a worst-case scenario in which emissions continue to increase without slowing, to an overly optimistic scenario that results in a world at +1.5°C. The reality is certainly between these two extremes.

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