“Human activities have caused a global temperature rise of 1.25°C and the current trajectory of emissions 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), introduce, in Science, their analysis of the efforts made by the international community since the Paris conference, in 2015. They also recall that the current trend is an increase of around 0.24°C per decade. In other words, the mass seems to be said concerning the most ambitious objective defined in Paris: to contain the rise in the average temperature “significantly below 2°C compared to pre-industrial levels”, while acting to limit this rise to 1, 5°C to “significantly reduce the risks and effects of climate change”.
“Optimism is not appropriate among scientists, underlines Samuel Jaccard, climatologist at the University of Lausanne and co-author of the. When we evaluate the non-binding promises made by countries, we see that they lead to a warming of more than 2°C in 2050. In addition, almost all countries do not respect their commitments.
In fact, assuming that we immediately stop emitting any greenhouse gases – which obviously will not happen – the 1.5°C threshold would still be crossed within a decade. “There is 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 which is just waiting to be returned to the atmosphere. “This is why we must not only reduce our emissions very quickly, but also implement solutions to capture atmospheric CO2.”
For Damon Matthews, there are still reasons for hope. “Over the past ten years, greenhouse gas (GHG) emissions have more or less stabilized. We are no longer on the worst-case scenario, which led to an increase in the average temperature of 4 to 5°C. The long-term trend today is more like 2 to 3°C, but we are very far from the objective of the Paris Agreements. Which assume that we achieve net zero greenhouse gas emissions over the coming decades, before we achieve net negative emissions – in other words, cleaning the atmosphere of part of the excess gas.
Pumping carbon, a solution worth several hundred trillions
This concept of net zero emissions must be well understood, insists Samuel Jaccard. “This does not mean that we no longer emit GHGs, because there are unavoidable emissions, such as those from agriculture, air traffic, for example. This means that these incompressible emissions must be compensated by actions that remove CO2 from the atmosphere, what are called negative emissions. For example by reforesting, encouraging the appearance of grasslands or even pumping the gas directly into the air to sequester it underground, like what the Swiss start-up Climeworks is doing in Iceland. “Today, it captures 4,000 tonnes per year, compared with the 70 million tonnes emitted by Germany’s largest coal-fired power station.” In other words, the Icelandic installation erases only 3.5 seconds of our annual CO2 emissions each year (around 36 billion tonnes in 2021)! All at a cost close to 1000 francs per ton, even if Climeworks hopes to bring it down to around 100 to 200 francs by 2035. However, several hundred billion tons of CO2 would have to be captured to sustainably contain the rise in temperature of the globe around 2°C… “There really is a problem of scale and it is hard to see how we can solve it in the short term”, regrets Samuel Jaccard.
Many countries have committed to reaching “net zero” in 2050 or 2060. Germany is an exception with a target of 2045. For Damon Matthews and Seth Wynes, 2040 should rather be targeted on a global scale. “This would only give a 50% chance of staying below 1.5°C, but more than 80% of not exceeding 1.75°C and more than 95% of staying below the 2°C threshold”, write they in Science. Two degrees that would lead to much more serious consequences than 1.5°C, particularly in terms of extreme events and the destruction of biodiversity, noted a special IPCC report devoted to this subject in 2018.
“We, the developed countries, have a historical moral responsibility vis-à-vis global warming, adds Samuel Jaccard. If the planet is to reach net zero in 2040, this means that we should do so as early as 2030 to leave some room for emerging countries. Looking at the policies put in place 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 hadn’t been for the Paris Accords. Science tells us that containing global warming is possible, even if it will be difficult. But there are many brakes in governments, industries and even in individuals. It is really necessary that everyone understands that it is necessary to act and to do it. Very quickly and strongly.” We bet that the multiplication of extreme events will do more for this awareness than these temperature thresholds which remain not very concrete for ordinary mortals.