Kommer klimatförändringen leda till fler och svårare översvämningar? Denna fråga behandlas IPCC AR6 i kapitel 8 (239 sidor) [1] och mer kortfattat i FAQ 8.2 (sida -119, 2 sidor).

IPCC anser att klimatförändringarna förväntas försvåra översvämningar. De påverkar redan var, hur ofta och hur kraftiga översvämningarna blir. Ändå kan översvämningar inom vissa områden bli mer sällsynta. Om luftens värme ökar med 1 grad ökar vattenmängden med 7%.

FAQ 8.2: Will floods become more severe or more frequent as a result of climate change?

A warmer climate increases the amount and intensity of rainfall during wet events, and this is expected to amplify the severity of flooding. However, the link between rainfall and flooding is complex, so while the most severe flooding events are expected to worsen, floods could become rarer in some regions.

Floods are a natural and important part of the water cycle but they can also threaten lives and safety, disrupt human activities, and damage infrastructure. Most inland floods occur when rivers overtop their banks (fluvial flooding) or when intense rainfall causes water to build up and overflow locally (pluvial flooding). Flooding is also caused by coastal inundation by the sea, rapid seasonal melting of snow, and the accumulation of debris, such as vegetation or ice, that stops water from draining away.

Climate change is already altering the location, frequency and severity of flooding. Close to the coasts, rising sea levels increasingly cause more frequent and severe coastal flooding, and the severity of these floods is exacerbated when combined with heavy rainfall. The heavy and sustained rainfall events responsible for most inland flooding are becoming more intense in many areas as the climate warms because air near Earth's surface can carry around 7% more water in its gas phase (vapour) for each 1°C of warming. This extra moisture is drawn into weather systems, fueling heavier rainfall (FAQ 8.2, Figure 1).

Texten fortsätter i AR6, Chapter 8.