Global climate change observations

Key points

We have clear evidence of human-caused climate change.
The Earth is warming rapidly. Both land and sea temperatures have increased over the past 100 years, and are increasing more rapidly.
Other changes and evidence of climate change are being observed. These include a reduction in the mass of global ice caps and glaciers, rising sea levels, acidification of our oceans, and increased frequency and intensity of extreme weather events.
These changes are expected to continue, even if we reduce our greenhouse gas emissions, because of existing emissions and changes to our climate systems.

Evidence of global warming

The Intergovernmental Panel on Climate Change (IPCC) has said that ‘it is unequivocal that human influence has warmed the atmosphere, ocean and land'.

The earth's average surface air temperature has risen by between 1.3 °C to 1.4 °C since the pre-industrial era. Most of the warming has occurred in the past 40 years, and each decade since 1980 has been warmer than the decade before. Globally, the past 11 years up to and including 2025 have been the warmest on record.

Our oceans have also warmed. The top 100 metres of ocean has warmed more than 0.33 °C since 1969, and the average sea-surface temperature in 2019 was second only to 2016, which was a record El Niño year.

Evidence of other changes

Our oceans have also warmed. The world’s oceans have taken up more than 90% of the extra energy on Earth from increases in greenhouse gas concentrations. Ocean warming varies between regions and depths, as heat absorbed at the surface is redistributed by ocean circulation. Ocean warming has been accelerating over the past two decades, with the 2005-2024 warming rate more than double that recorded during 1960-2025.

Reduced ice and snow

The ice sheets and ice shelves in Greenland and Antarctica are melting due to a warmer climate. In 2023, the Antarctic ice sheet had record low summer sea ice extent. Antarctic and Arctic sea-ice extent continued to be below average in 2025. Reduced sea-ice coverage can change ocean circulation, impacting how much heat and carbon the ocean can absorb from the atmosphere.

Globally, mountain glaciers and snow cover have declined in all monitored regions and are very likely to continue declining. The mass loss rate of glaciers recorded between October 2023 and September 2024 was more than double the annual average loss rates of the last twentieth century.

Rising sea levels

Sea levels are rising primarily because ocean water expands as it warms (thermal expansion), and because melting glaciers and ice sheets add water to the oceans.

Globally, mean sea level has risen about 20 centimetres in the past 100 years and the rate of rise has accelerated in recent decades. Over the past 3 decades, global mean sea level has risen by approximately 9-10 cm, reflecting the accelerating rate of sea-level rise.

Ocean acidification

Some of the increased levels of carbon dioxide in our atmosphere dissolve in the ocean, which makes the water more acidic. Since the 1880s, the acidity of surface ocean waters globally has increased by about 30% (0.1 pH units).

Increased extreme events

Climate change is making some extreme weather events more frequent and more intense. Extreme weather and climate-related events such as destructive rainfall, floods, sweltering heat, and wildfires have damaged cropland, eroded livelihoods, and displaced people across multiple regions worldwide, including many parts of Australia.

Current global outlook

Even if we reduce our greenhouse gas emissions, global temperatures will continue to rise for decades to come. Global warming of 1.5 °C and 2 °C will be exceeded during the 21st century unless deep reductions in greenhouse gas emissions occur in the coming decades. The global ocean will continue to warm, mostly in tropical and subtropical regions. There will be more frequent hot, and fewer cold temperature extremes across most land areas.

The IPCC reports that the net damage costs of climate change are likely to be significant and to increase over time. Adaptation will be needed to reduce the impact of unavoidable warming.