Containing global warming to 1.5°C seems out of reach

“Human activities have caused a global temperature increase of 1.25°C and the current emissions trajectory suggests that we will exceed 1.5°C in less than ten years.” This is how Damon Matthews and Seth Wynes, from Concordia University in Montreal (Canada), present, in Science, their analysis of the efforts made by the international community since the Paris conference in 2015. They also point out that the current trend is an increase of approximately 0.24°C per decade. In other words, the mass seems to be said in relation to the more ambitious goal set in Paris: containing the increase in average temperature “significantly below 2°C relative to pre-industrial levels”, acting to limit this increase to 1.5 °C 5°C to “significantly reduce the risks and effects of climate change”.

“Optimism is inappropriate among scientists,” stresses Samuel Jaccard, a climatologist at the University of Lausanne and co-author of the latest report by the Intergovernmental Panel on Climate Change (IPCC). When we look at the non-binding pledges made by countries, we see that they lead to warming of more than 2°C by 2050. Furthermore, almost all countries do not respect their commitments.

In fact, assuming we immediately stop emitting any greenhouse gases – which we obviously won’t – the 1.5°C threshold would still be exceeded in a decade. “There’s a lot of inertia in the climate system,” recalls Samuel Jaccard. The oceans have indeed accumulated extraordinary amounts of heat. In addition, they also contain a lot of CO2 that they have captured and that is just waiting to be returned to the atmosphere. “That’s why we must not only reduce our emissions very quickly, but also implement solutions to capture atmospheric CO2.”

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For Damon Matthews, there is still reason for hope. “Over the past ten years, greenhouse gas (GHG) emissions have more or less stabilized. We are no longer in the worst case scenario, which has led to an average temperature increase of 4 to 5°C. The long-term trend today is more than 2-3°C, but we are a long way from the Paris Agreements objective. Which assumes that we reach zero net greenhouse gas emissions in the next few decades, before we hit net negative emissions – in other words, clearing the atmosphere of some of the excess gas.

Pumping carbon, a solution worth several hundred trillion

This concept of net zero emissions must be well understood, insists Samuel Jaccard. “This does not mean that we do not emit more GHGs, as there are unavoidable emissions, such as those from agriculture, air traffic, for example. This means that these incompressible emissions must be offset by actions that remove CO2 from the atmosphere, the so-called negative emissions. For example, reforesting, encouraging the emergence of pastures or even pumping the gas directly into the air to sequester it underground, like what the Swiss startup Climeworks is doing in Iceland. “Today, it captures 4,000 tonnes a year, compared to the 70 million tonnes emitted by Germany’s largest coal-fired power plant.” In other words, the Icelandic facility erases just 3.5 seconds of our annual CO2 emissions each year (about 36 billion tonnes in 2021)! All at a cost close to SFr1,000 per ton, even if Climeworks hopes to reduce it to around SFr100-200 by 2035. However, several hundred billion tons of CO2 would have to be captured to sustainably contain the increase in global temperature around 2°C… “There is really a problem of scale and it’s hard to see how we can solve it in the short term”, laments Samuel Jaccard.

Many countries have committed to reaching “net zero” by 2050 or 2060. Germany is an exception with a target of 2045. For Damon Matthews and Seth Wynes, 2040 should be a target on a global scale. “This would give only a 50% chance of staying below 1.5°C, but over 80% of not exceeding 1.75°C and more than 95% of falling below the 2°C threshold,” they write in Science. Two degrees that would have far more serious consequences than 1.5°C, particularly in terms of extreme events and destruction of biodiversity, noted an IPCC special report devoted to this issue in 2018.

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“We developed countries have a historic moral responsibility in relation to global warming,” adds Samuel Jaccard. If the planet reaches net zero by 2040, that means we should do it as early as 2030 to leave some room for emerging countries. Looking at the policies implemented in our economies, including Switzerland, the account will not be there. Not to mention the consequences of geopolitical events: the German environment minister, an environmentalist, has just announced that his country will have to relaunch coal to reduce its dependence on Russian gas…

“Of course, there are many reasons not to be optimistic, insists Damon Matthews. But imagine where we would be if it weren’t for the Paris Accords. Science tells us that containing global warming is possible, even if it is difficult. But there are many brakes on governments, industries and even individuals. It is really necessary for everyone to understand that it is necessary to act and do it. Very fast and strong.” We’re betting that the multiplication of extreme events will do more for this awareness than these temperature thresholds that remain unclear to ordinary mortals.

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