Global climate monitoring

Como funciona: AMOC combines surface and deep currents, transporting heat northward. Temperature and salinity influence water density and deep-water formation.

O que pode mudar: warming and freshwater input may weaken this circulation. A strong change would affect heat distribution, precipitation and regional sea level.

Portugal e Europa: effects depend on the strength of the change and global warming. A weaker AMOC does not, by itself, imply a new ice age.

Incerteza: the date of a possible collapse is not established. An Atlantic temperature anomaly alone does not measure AMOC strength.

O que acompanhamos: the circulation intensity measured by ocean observing networks, heat transport, and changes in temperature and salinity. Sea surface temperature is only one part of this system.

Land ice: continental ice sheets differ from the sea ice shown in this page's charts. Loss of land ice adds water to the ocean.

Amplifying processes: in Greenland, decreasing ice elevation can favour further melting. In Antarctica, the ocean can accelerate ice loss in vulnerable sectors, including parts of West Antarctica.

Escala temporal: uma mudança desencadeada pode produzir efeitos durante séculos ou milénios; isso não implica o desaparecimento imediato dos mantos de gelo.

Incerteza: thresholds and rates vary between regions and processes. A single year of ice loss does not demonstrate that an irreversible threshold has been crossed.

O que acompanhamos: ice-sheet mass balance, glacier speed and contribution to sea level. Sea ice extent cannot replace these measurements.

Um ciclo interligado: the forest stores carbon and returns water to the atmosphere through evapotranspiration, contributing to regional rainfall.

O que pode mudar: tree loss and persistent droughts can reinforce each other, favouring forest degradation and a transition to other vegetation types in some areas.

Incerteza: the response varies across the Amazon and also depends on land use. There is no single confirmed date for a change affecting the entire forest.

O que acompanhamos: forest cover loss, drought duration, fires and vegetation recovery. These indicators should be considered together and over several years.

Carbono armazenado: when soil thaws, microorganisms can decompose previously frozen organic matter, releasing CO₂ and, under some conditions, methane.

Regional changes: thaw can be gradual or locally abrupt, changing the ground, drainage and ecosystems.

An important distinction: this warming feedback does not imply a single global threshold at which all permafrost thaws at once. Regional processes and vulnerabilities differ.

Escala temporal: recovery of lost carbon is slow. The amount and rate of emissions remain uncertain.

O que acompanhamos: soil temperature, seasonal thaw-layer depth and changes to the ground. Measuring thaw and estimating carbon emissions are different tasks.