Melting and consequences

A major concern

Changes in the oceans and frozen regions are the subject of a special report by the Intergovernmental Panel on Climate Change (IPCC). The report, published on the 25th of September, calls for ambitious measures and highlights “the ever-increasing risks of inaction”.

The number of people affected is considerable: 680 million people live in coastal regions at less than 10 metres above sea level. The Arctic alone has a population of 4 million, which is already facing significant upheavals. Not forgetting the 65 million inhabitants of small island developing states, some of which are at risk of being wiped off the map by rising sea levels.

However, other types of environments are also examined by the report: in high mountains, 670 million people live in the proximity of glaciers and their precious freshwater reserves.

A specific threat

The consequences of climate change are well documented. The oceans are warming, the ice is melting, the sea level is rising, and the pace is accelerating. Water levels have increased by about 15 cm over the past century. The levels are now growing at a rate of 3.6 mm per year. The inertia of the Earth’s climate system means that this phenomenon can no longer be stopped, even in the most optimistic scenarios. If the Paris Agreement objective of limiting warming to below 2°C is achieved, the oceans will still swell by between 30 cm and 60 cm by the end of the century.

Extreme weather events are increasing in frequency and intensity: heavy rains, tropical cyclones, floods, or – at the opposite extreme – heatwaves and prolonged droughts. The increase in the humidity over the ocean, a consequence of warming, plays a vital role in this phenomenon.

At the same time, biodiversity is declining, and the oceans’ food resources are being depleted. The seas are becoming more acidic, less rich in oxygen, and the supply of nutrients from the deep decreases as warming slows down the water’s mixing. Climate change is also shifting fish populations from tropical regions to colder areas, which may be suitable for some areas, such as the Arctic, but raises fears of hardship for many communities dependent on traditional fisheries.

In the high mountains, the risks include a decrease in water resources and an increase in natural disasters: landslides, avalanches and floods. The consequences of water scarcity extend to agriculture, hydroelectric power generation and income derived from tourism.

Depending on the scenarios considered, between 25% and 70% of the surface permafrost (3 to 4 metres thick) is expected to melt by 2100, releasing large quantities of carbon dioxide and methane – a potent greenhouse gas – into the atmosphere.

A political emergency

The report’s conclusions are clear: there is an urgent need to reduce greenhouse gas emissions drastically. Otherwise, we will face even more difficult challenges: land submergence, migration, food security, access to drinking water, economic difficulties in many sectors, deteriorating health, damage to cultural values and people’s identity.

The IPCC report provides a sound scientific basis for the discussions at COP25. The conference will be held in Chile in December this year. Will the commitments match the stakes?