09 Aug IPCC: Unparalleled Climate Change Leads to Significantly More Weather Extremes
The rate at which the climate is changing is unprecedented in at least two thousand years and possibly much longer. In addition, some aspects of climate change risk becoming irreversible for a period of centuries or even thousands of years, such as rising sea levels. Without drastic measures, the world must prepare for much greater weather extremes.
This is according to the latest report from the IPCC, the climate panel of the United Nations. Several hundred climate scientists from 66 countries have worked on it for years. It serves as the basis for climate policy by governments worldwide, and comes just before the global political climate summit in Glasgow next autumn.
Since the previous regular IPCC report in 2013, knowledge about the climate has increased considerably. According to the climate scientists, it is clear that global warming has already led to major changes: in the atmosphere, on land and in the oceans.
Warming has an effect on weather extremes and the evidence for this is stronger than in the previous report, according to the IPCC. These include heat waves, heavy rainfall, extreme drought and tropical cyclones. The report also states that oceans are warming at an unprecedented rate.
Over the past two weeks, government delegations from around the world have agreed word for word on a summary of the IPCC report. Scientists had a constant veto on this, if they believed the much more extensive underlying report — spanning thousands of pages — was violated. This state of affairs is always the same. The idea is that countries will embrace the report and use it as the basis for their climate policy.
If the earth warms further, this will lead to even greater changes in the climate. That mainly means:
- More intense and frequent heat waves
- More heat waves in the oceans
- More and more heavy rain
- More frequent drought
- More severe tropical cyclones
- Less and less ice at the North Pole
- Decrease in permafrost
The Earth has warmed by just over one degree since the pre-industrial era. In any case, according to the report, warming will continue until the middle of this century, even if it is possible to drastically limit emissions of CO2 and other greenhouse gases. Only if drastic and large-scale measures are taken quickly will a limitation to 1.5 or two degrees of warming be possible, the IPCC says.
For the Netherlands, insights into sea level rise are especially important. It goes faster and faster. Between 1901 and 1971 it was 1.3 millimeters per year, then until 2006 it became 1.9 and then the increase increased to 3.7 mm per year (until 2018).
As a result, sea level rise is now most likely faster than at any time in at least the past three thousand years. How much more this will be in the future depends mainly on how soon it will be possible to reduce emissions. Scenarios show that the average sea level rise at the end of this century varies between a few decimeters to just over a meter (1.01 m).
The UN climate panel IPCC publishes a voluminous report in three parts every few years, the last time was in 2013. This first part contains the scientific basis on climate change. Part two and three will be published next year, about the consequences of climate change and the possibilities for reducing greenhouse gas emissions as quickly as possible.
If everything goes wrong and greenhouse gas emissions remain high, the sea level will continue to rise. In the year 2100 it can be a maximum of two meters, in 2150 five meters. But, the report states, a much higher sea level rise is also possible “in a scenario with very high greenhouse gas emissions”. This scenario of two meters by the end of this century, five meters in 2150 and fifteen meters in 2300 is not very reliable, but “cannot be ruled out because of the great uncertainty in ice sheet processes”.
New in this IPCC report is that more attention has been paid to regional differences. The Earth’s climate does not change in the same way everywhere. For example, the Mediterranean is mentioned as one of the areas at risk of extremely high temperatures in the future.
Moreover, there is now more clarity about the so-called climate sensitivity. That is, the extent to which the climate responds to a certain amount of emissions. The chance that this effect will not be too bad has decreased considerably.
It also discusses possible tipping points in the climate, such as the collapse of one of the large ice sheets or abrupt changes in ocean currents. The chance of this is considered very small, but it cannot be ruled out either.