For the first time, IPCC climate experts are reporting on the oceans and the cryosphere. The impact of global warming on the oceans, polar ice caps and glaciers is overwhelming: more than 1.4 billion people are potentially directly affected.
“Our emissions of greenhouse gases have a footprint that goes from the high mountains to the bottom of the oceans,” says Valérie Masson-Delmotte, paleoclimatologist at the CEA and vice-president of the IPCC, to summarize this new special report from the group of intergovernmental experts on global warming.
For 3 years, about a hundred researchers have reviewed 7000 scientific publications for this mega-synthesis of the latest knowledge on the state of the oceans and the cryosphere, that is to say the frozen areas: glaciers, ice pack, ice caps, permafrost. These parts of the world covered with snow or ice represent 10% of the planet’s surface. The 40-page summary for policy makers is being released this Wednesday, September 25. And without surprise, the report is overwhelming.
Sea level rise has been accelerating in recent decades, mainly due to melting ice in Greenland and Antarctica, glacier retreat, but also ocean dilation (when they warm up, they take up more space). The pace of this climb is 2.5 times higher than during the period 1901-1990. Today, the rise of water is on average of 3.6 mm, against 1.4 mm over the period 1901-1990.
Experts have revised upwards their projections for the end of the century, if emissions continue to rise very strongly (the worst case scenario), the sea level could rise by 1.10 meters by 2100.
At this slow and steady rise in sea level, there is a more specific danger for people living in coastal areas and small island states: a surge of water, linked to extreme weather events that will multiply. The hurricanes in the Pacific act like battering on the coast, explains Hélène Jacot des Combes. This paleocenographer is a professor at the University of the South Pacific: “We have information in this report that tells us that extreme events, such as coastal flooding, which are now observed once a century, could become more frequent and occur once a decade, or even in some extreme projections, once a year.”
In the Arctic, the surface of the ice pack at the lowest level since 1000 years
This month of September 2019, the size of the ice pack in the Arctic has shrunk again: it is the second lowest area observed in 40 years of satellite measurements, behind the record of 2012. The report of the IPCC confirms this trend. Experts estimate that it is almost certain that the ice pack surface in September will decrease by 12.8% per decade. “These changes in ice cover in September are likely unprecedented for 1000 years,” the report says.
At the same time, the icecaps of Greenland and Antarctic lose billions of tons of ice a year. The loss of mass in Greenland has doubled over the last two decades and has tripled in Antarctica. Researchers are now wondering whether the melting of Antarctica, an even larger ice reservoir than the North Pole, will become the main cause of rising sea levels, but with no certainty today. “There is an acceleration of the flow in the West Antarctic”, explains Valérie Masson-Delmotte. “But the report can not say whether this is the beginning of irreversible instability.”
Glaciers are receding almost everywhere in the world. By 2100, the glaciers of Central Europe, the Caucasus, North Asia, Scandinavia, the tropical Andes, Mexico, East Africa and Indonesia could lose 80% of their mass according to the most pessimistic projections on the level of CO2 emissions. Some may disappear even if emissions fall.
In the mountains, an essential adaptation
In the high mountains, the evolution of glaciers has a considerable impact on local populations, says the report. Beyond the risk of natural disasters (landslides) the timing and the level of flow of the rivers will be modified. It will therefore be necessary to review the management of drinking water and the resource for irrigation, explains Valérie Masson Delmotte. “In Asia, around the Himalayas and Tibet in particular, it has consequences for the freshwater resource for about a quarter of the world’s population who live in the watersheds fed by the melting of snow and ice during the dry season.”
This report is also concerned about permafrost thaw. Frozen soil surfaces on the earth’s surface could decrease by 30 to 99 percent from today’s worst-case scenario. But they are gigantic reservoirs of carbon and methane, they could release tens, even hundreds of billions of tons of greenhouse gases in the atmosphere. And so aggravate the climate crisis.
The melting of glaciers, ice caps, thawing of permafrost, will continue in the short term, experts say. More difficult to predict after 2050, everything will depend on the efforts made (or not) to reduce emissions of greenhouse gases.
The oceans, a climate regulator in crisis
The oceans, which cover 2/3 of the planet, do us good services. They provide us with oxygen, pump about 30% of the CO2 emitted by the human activities in the atmosphere, and have absorbed 90% of the increase in temperature since it was recorded. But this formidable climate machine is tired. By absorbing much of the heat and carbon, the oceans get warmer (ocean warming has more than doubled since 1993), more acidic, saltier and less oxygen-rich.
Among the consequences detailed for the first time by this IPCC report: marine heat waves, are likely to become 20 times more frequent (than in 1982) in the case of warming to 2°C (50 times more frequent in the most pessimistic scenario). These heat waves at sea have an impact on biodiversity (in particular on the distribution of fish and the balance of ecosystems), and indirectly on the coastal populations who draw their resources from the sea.
“These heat waves have an effect on the tropical coral reefs,” says Helene Jacot des Combes, a professor at the University of the South Pacific, co-author from the report. “But many small island states depend on these reefs for fishing but also as natural barriers to protect themselves from the onslaught of the ocean, and good reef health is also vital for the tourism sector.”
On the thorny issue of immigration caused by the climate crisis, the report does not quantify the number of potentially displaced people. The study mentioning 280 million affected individuals was not included in the final version of the report.
One of the authors of the report, Hélène Jacot des Combes, explains that this figure was not corroborated. On the other hand, “it is shown that the retreat of glaciers in certain regions, and especially around Tibet, in tropical regions but also in Alaska, leads to the departure of local populations.”
Today, the consequences of global warming on the oceans and frozen areas (the cryosphere) directly affect 1.4 billion people living on the coast (680 million people today, 1 billion in 2050), in high mountains (670 million inhabitants), in the small island developing states (65 million inhabitants) without counting the 4 million inhabitants of the Arctic.
This report once again rings the alarm for governments to drastically reduce greenhouse gas emissions, and thus limit this major upheaval in progress. But this very detailed block, region by region, also aims to help decision-makers choose the best solutions to help local people adapt to what lies ahead and the already well known global warming.
Greta Thunberg, of the most active young militant against global warming had made a very strong speech at the UN climate summit earlier this week, check it out.