Abstract
The ocean has so far acted as a buffer against climate change, taking up more than 90% of the excess heat in the climate system. Climate change now alters the ocean in many ways with sweeping and severe consequences for nature and humanity. Increasing sea level, from rising sea temperatures and 100s of gigatonnes of melting ice from land, is a severe treat to 700 million people in the low-lying coastal zone. In the Arctic declining sea ice disrupts people and ecosystems, while also causing opportunities for shipping and fisheries.
Ocean warming affects marine live in many ways. It reduces mixing between water layers and therefore the supply of oxygen and nutrients. Marine heatwaves are becoming more frequent and strong, especially harming warm-water corals and kelp forests. Warmer seas affect the distribution of marine life and changes carrying capacity and established phenological patterns. Increasing ocean acidity is expected to affect keystone marine species and thus ecosystems negatively.
The United Nations’ and World Meteorological Organization’s Intergovernmental Panel on Climate Change (IPCC) is the world’s leading source for authoritative information on climate change. IPCC assesses literature, evaluates risks, suggests strategies for adaptation and provides decision makers with thorough and balanced advice, following rigorous review processes. In September 2019, IPCC launched SROCC where I was one of the lead authors. Here I will talk about main results, as outlined above.
Geir Ottersen
Webpage at IMR
Webpage at CEES, IBV, UiO