After decades of warning, a team of scientists has just estimated that the Arctic could be deprived of summer sea ice (ice sheet) as early as the 2030s. “This is about a decade earlier than the latest IPCC forecasts,” points out Seung-Ki Min, co-author of the article. This would be the case even in a low greenhouse gas emissions scenario.
What does this new study say about the Arctic?
We know that the area of Arctic sea ice has been shrinking for decades, with a sharper decrease since 2000. In contrast, using observational data from 1979 to 2019 to run new simulations, the team of scientists indicate that the first month of September is without sea ice already exist in the years 2030-2050, regardless of the emission scenarios.
Projections of Arctic sea ice at different levels of warming, illustrated here by SSP scenarios.
source
An important fact that will not please Climate skeptics unleashed themselves on social networks since the announcement: It is indeed human activities and greenhouse gases that are largely responsible. Aerosol, solar, and volcanic activity have a far smaller contribution.
Cowardly. 1: Time series of observed and simulated Arctic sea ice area (SIA) and their linear trends.
Source: Observational projections of an ice-free Arctic even under a low emissions scenario
Why is September a reference month? Arctic sea ice reaches its minimum annual area at the end of summer, in September, according to the 2021 IPCC report. In addition, in 2021 (i.e. after the publication of Part 1 of the last IPCC report), Arctic sea ice was at the second lowest level on record.
Figure 9.13 – Historical Arctic sea ice data and forecasts from Phase 6 of the Coupled Model Intercomparison Project (CMIP6)
Source: IPCC Chapter 9, Working Group 1 / 6th Report, page 38
10 years earlier than expected
The IPCC Sixth Assessment Report projects that the Arctic is projected to be, on average, nearly ice-free (less than 1 million km² of sea ice) by mid-century under low-carbon scenarios. Medium and high greenhouse effects, but not under low-emission scenarios. This is the big difference and the novelty that this study proclaims.
“This is about a decade earlier than the IPCC’s most recent projections,” said UN-commissioned group of climate experts Seung-Ki Min from South Korea’s Pohang and Yonsei Universities, co-author of the article.
It is important to understand that “the first year without sea ice will not necessarily be a point of no return,” oceanographer and climatologist Jean-Baptiste Sallée, co-author of the latest IPCC report, points out in Le Figaro. “We have to distinguish between a one-off event and an ice-free summer that repeats itself over several years and is classified as a ‘response to climate change’. If ice-free summers are the norm, then we have reached a point of no return, or almost, and the only way to turn it around is to lower the global temperature.”
Is the Arctic sea ice a turning point?
It is possible that the communication is a bit confused as to the term “tipping point” or tipping point in English. Some people communicated about it being a turning pointothers do not, and it is important to define the term well.
What is a turning point?
Although the principle has been known to scientists for several decades, the tipping point has only recently been used explicitly. The IPCC refers to it for the first time in its 4th report and now refers to it in every report (and special reports). In Special Report 1.5, the turning point is defined as follows:
Degree of change in the properties of a system at which the system reorganizes, often abruptly, and does not return to its original state, even when the changing factors are removed. In relation to the climate system, the tipping point refers to a critical threshold above which the global climate or a regional climate changes from a transition from one stable state to another stable state.
The second very important concept is this“Irreversibility”. : “Term denoting the perturbed state of a dynamical system on a specific time scale when the time required for the system to be restored by natural processes is significantly longer than the time required to reach that perturbed state .”
note that These tipping points can be caused by either natural climate variability or external influences such as global warming.e. These tipping points, which are plausible to occur within the next century or two (or even earlier) due to anthropogenic emissions, are likely to result in irreversible evolution. It would then take centuries, even millennia, before the initial situation was reached again.
What are the different turning points?
These tipping points are numerous and varied: we find, of course, the Amazon forest, but also the melting of the Arctic sea ice, the partial (Antarctic) or complete (Greenland) melting of the ice caps, changes in the thermohaline circulation, the transformation from the Amazon forest to the savannah, the weakening of the Indian summer monsoon, thawing of the permafrost (which would release greenhouse gases), etc.
In 2018, Steffen & al. published a map summarizing the major theoretical turning points above a certain level of mean global warming when summer sea ice was present in the Arctic:
Global map of possible cascading tipping points
Source : Will Steffen et al. PNAS 2018
Can we say that Arctic sea ice represents a turning point?
Dirk Notz, co-author of the study, said: “This will be the first major component of our climate system that we lose through our greenhouse gas emissions.”
But the IPCC, in its most recent report, notes that summer sea-ice loss in the Arctic is not a turning point (high confidence, page 5 of chapter 9). This is what McKay & al. in their study published in September 2022, which ruled out the Arctic sea ice tipping point.
Jean-Baptiste Sallée also confirms this: According to the IPCC definition, this is not a turning point, because if we reduce global warming, the ice will come back. On the physical level it is very clear. If some people see this as a turning point, it’s probably because global warming won’t stop and government promises lead us to global warming well above +2°C (potentially +4°C in France) and since then promises only bind those who believe them…
NB: It is also very important to understand that These tipping points are difficult to define precisely, and once triggered, they do not necessarily result in an abrupt and immediate change in climate : Once the “threshold” is crossed, the change is clearly felt, but the consequences can stretch for centuries or even millennia, as in the case of sea level rise.
What are the possible consequences of summers without sea ice in the Arctic?
Without hesitation, the most important consequence will be an increase in extreme weather events that we are currently experiencing, such as heat waves, wildfires and floods, said Seung-Ki Min, who led the study. “We must be more ambitious in reducing carbon emissions and prepare for faster warming of the Arctic and its impact on human society and ecosystems.”
The phenomenon will also accelerate warming in the Arctic, which “may exacerbate extreme mid-latitude weather events, such as heat waves and wildfires.” It could also accelerate global warming from thawing permafrost, as well as sea-level rise from melting Greenland ice sheet.”
Jean-Baptiste Sallée recalls in Le Figaro: “The ice floe reflects the sun’s rays. Its disappearance will increase global warming, with the risk of triggering a vicious cycle “that could affect the Greenland ice cap, for example.”
The consequences reach far beyond the Arctic
This ice cap contains enough ice to raise the sea level by six to seven meters, specifies Heïdi Sevestre, glaciologist for Bon Pote. And among the other consequences we could also mention:
Finally, the lead author of the study also points out that sea ice is “a driving force of global ocean circulation”: Even its disappearance for one or more months could have consequences that are difficult to assess today.
It’s too late to save the Arctic’s summer sea ice
“It’s too late to save summer sea ice in the Arctic.” This statement is spine-chilling and should be front-page news. If disasters are to be fought because they can lead to inaction, this new study is likely to be the most publicized event of the year given the serious consequences it will have for humanity. As an aside, note that not only is the Arctic suffering, but Antarctica is also in a very bad state.
Antarctic sea ice extent anomalies for each year from 1979 to 2023 (Satellite Age; NSIDC, DMSP SSM/I-SSMIS). Anomalies are calculated using a 5-day moving average of the 1981-2010 climatological baseline. The year 2023 is represented by a red line (updated 06/05/2023).
“Scientists have warned of these disappearances for decades, and it is sad to see that those warnings have largely gone unheeded,” said the study’s lead author. Everyone should remember that. Scientists are not listened to, they are even deliberately ignored.
No government in the world has a plan to honor the Paris Agreement and we even have Emmanuel Macron allowing statements like “Who could have predicted the climate crisis?”. As the IPCC reminds us that our climate future is in our hands, there is an urgent need for our leaders to take their responsibilities and organize a drastic and rapid reduction in fossil fuel use.
For millions of people, it is a matter of life and death in the short term, and promises have no impact on global warming: only actions count.