The reports from the Intergovernmental Panel on Climate Change (IPCC) provide a synthesis of the current and future climate changes at the global scale, based on the most recent peer-reviewed literature. Additional reports also fill the gaps between the different IPCC reports. I tried to highlight the key points of some of the most recent reports below. More information can be found on the official website: https://www.ipcc.ch/.
On 19 June 2025, Forster et al. (2025) published an annual update of they key indicators of the state of the climate system. This annual report allows to fill the gap between the IPCC AR6 (published in 2021) and AR7 (expected in 2028). A nice user-friendly data dashboard accompanies the report. Key results include:
Global mean surface air temperature has increased by 1.24°C over the last decade (2015-2024) compared to pre-industrial levels (1850-1900). 2024 became the first year since pre-industrial times to exceed the +1.5°C (+1.52°C more exactly).
The increase in temperature is mainly driven by anthropogenic greenhouse gas emissions, as well as a reduction in the strength of aerosol cooling. Average annual greenhouse gas emissions for 2014-2023 are 54 Gt CO2, of which 68 % comes from fossil-fuel CO2 emissions (coal, oil and gas + industrial processes), and the rest is from land-use change and forestry CO2 emissions (6%), CH4 emissions (17%), N2O emissions (5%), and fluorinated gases (3%).
The remaining carbon budget to stay under +1.5°C global warming is 130 Gt CO2 (50% likelihood), i.e. about 3 years from now with the current emission level (~ 40 Gt CO2 / year). For staying under +2°C global warming, the remaining carbon budget is 1050 Gt CO2 (50% likelihood), i.e. the budget would be exhausted in 2051.
The global sea level has risen by 23 cm since the start of the 20th century with a current rate of sea-level rise of 4.3 mm/year.
The WGI of the AR6 focuses on the latest findings in terms of the physical science basis of climate change. The main conclusions include:
Human influence has warmed the climate at a rate that is unprecedented in at least the last 2000 years.
Global surface temperature has increased by 1.1°C between 1850-1900 and 2011-2020, with larger increases over land (+1.6°C) than over the ocean (+0.9°C).
Greenhouse gases are the main drivers of tropospheric warming.
Precipitation over land has increased since 1950.
Glaciers and ice sheets have retreated since the 1990s and Arctic sea-ice area has decreased since 1979.
The global upper ocean has warmed since the 1970s.
As a result of thermal expansion of the ocean (50%), melting glaciers, ice sheets and glaciers (42%), and changes in land water storage (8%), global mean sea level has risen by 20 cm between 1901 and 2018. The current rate of sea-level rise is close to 4 mm per year.
Human-induced climate change is already affecting many weather extremes across the world.
Heat waves have become more frequent and more intense across most land regions since the 1950s, while cold waves have become less frequent and less severe.
Marine heat waves have doubled in frequency since the 1980s.
Heavy precipitation events have increased since the 1950s over most land areas.
The proportion of major tropical cyclones has increased over the last 4 decades.
Global surface temperature will continue to increase until at least 2050 under all emission scenarios considered. After that, results will depend on the greenhouse gas emission scenario followed.
The AR6 report assesses results from climate models participating in the Sixth Coupled Model Intercomparison Project (CMIP6). These models include a better representation of physical, chemical and biological processes (including cloud representation), as well as a higher resolution, compared to models considered in previous IPCC reports.
Climate model simulations used in the AR6 were done based on Shared Socioeconomic Pathways (SSPs) and radiative forcing levels.
Compared to 1850-1900, global surface temperature averaged over 2081-2100 will be higher by 1-1.8°C in the lowest emission scenario (SSP1-1.9), 2.1-3.5°C in an intermediate emission scenario (SSP2-4.5) and 3.3-5.7°C in the largest emission scenario (SSP5-8.5).
Future related climate changes include increases in the frequency and intensity of heat waves (both on land and oceans), heavy precipitation (+7% for each 1°C warming) and droughts, and reductions in Arctic sea ice, land ice, snow cover and permafrost.
With increasing CO2 emissions, ocean and land carbon sinks are projected to be less effective at slowing the accumulation of CO2 in the atmosphere.
For scenarios with higher CO2 emissions, the amount of emissions taken up by ocean and land carbon sinks is larger, but a large amount of emissions remains in the atmosphere. This means that the proportion of CO2 emissions taken up by land and ocean carbon sinks is smaller in high-emission scenarios.
The magnitude of feedbacks between climate change and the carbon cycle becomes larger but also more uncertain in high CO2 emissions scenarios.
Many changes due to greenhouse gas emissions are irreversible for centuries to millennia.
Increase in global ocean temperature, deep ocean acidification and deoxygenation are irreversible for centuries to millennia.
Mountain and polar glaciers will continue melting for decades or centuries.
The Greenland and Antarctic ice sheets will continue to lose ice through the 21st century.
Arctic sea-ice area will stabilize around 2 million km2 in the lowest emission scenario and will be lower than 1 million km2 in intermediate and high emission scenarios.
Global mean sea level will continue to rise over the 21st century, with large variations across the different emission scenarios, i.e. a rise of 28-55 cm in the lowest emission scenario and 63 cm - 1 m in the largest emission scenario. Over the next 2000 years, global mean sea level will rise by 2-3 m if warming is limited to 1.5°C, 2-6 m if limited to 2°C and 19-22 m with 5°C of warming, and it will continue to rise over subsequent millennia.
Limiting human-induced global warming to a specific level requires limiting cumulative CO2 emissions, reaching at least net zero CO2 emissions, along with strong reductions in other greenhouse gas emissions.
There is a near-linear relationship between cumulative anthropogenic CO2 emissions and global warming: each 1000 GtCO2 of cumulative CO2 emissions causes a 0.27-0.63°C increase in global surface temperature.
Our remaining carbon budget to limit global warming to 1.5°C relative to 1850-1900 is 400 GtCO2 (67% probability), consistent with SR15. To limit it to 2°C, our remaining carbon budget is 1150 GtCO2 (67% probability).
If global net negative CO2 emissions were to be achieved, the global CO2-induced surface temperature increase would be gradually reversed but other climate changes would continue in their current direction for decades to millennia. For instance, it would take several centuries to millennia for global mean sea level to change its course.
It would take about 20 years to see the effect of emission reductions on the global surface temperature due to climate natural variability.
Reductions in greenhouse gas emissions also lead to air quality improvements.
More detailed information about the AR6 can be found on the IPCC website and an excellent summary is provided by Carbon Brief.
You can also find this EGU Cryoblog post that summarizes results from the cryosphere components in the IPCC AR6 report.
The SROCC report focuses on the current and future climate changes occurring in the oceans and cryosphere (the frozen part of our planet, including ice sheets, ice caps, glaciers, snow, permafrost, sea ice, frozen rivers and lakes). The oceans and cryosphere play an important role for humans on Earth, as 680 million people live in low-lying coastal areas, 670 million people live in high mountain regions, 65 million people live in small island developing states, and 4 million people live in the Arctic region. They are also key components in the global climate, as the global ocean covers 71% of the Earth's surface and contains 97% of the water on Earth, and ice sheets and glaciers cover 10% of the Earth's land surface. Here are some key messages from the SROCC, focusing on physical changes:
Main recent changes affecting the cryosphere:
The combined ice mass from the Antarctic and Greenland Ice Sheets and glaciers was lost at a rate of 653 Gt per year between 2006 and 2015, equivalent to 1.81 mm per year sea-level rise (360 Gt ice correspond to 1 mm sea level). The different contributions are:
Antarctic Ice Sheet (largest ice sheet on Earth): ice loss of 155 Gt per year (0.43 mm sea-level rise equivalent), mostly due to rapid thinning and retreat of major outlet glaciers in the West Antarctic Ice Sheet
Greenland Ice Sheet (second largest ice sheet on Earth): ice loss of 278 Gt per year (0.77 mm sea-level rise equivalent), mostly due to surface ice melting
glaciers around the world: ice loss of 220 Gt per year (0.61 mm sea-level rise equivalent).
The Arctic June snow cover extent on land declined by 13% per decade between 1967 and 2018 (i.e. total loss of 2.5 million km2), mostly due to surface air temperature increase.
The temperature of permafrost increased by 0.29°C from 2007 to 2016.
The Arctic sea-ice extent decreased during all months between 1979 and 2018, with the most pronounced decline in September (- 13% per decade). No statistical trend was found during the same time period for the Antarctic sea-ice extent.
The areal proportion of multi-year Arctic sea ice (i.e. more than 5 years old) has decreased by 90% between 1979 and 2018.
Ice-albedo and snow-albedo feedbacks contributed to Arctic amplification, with Arctic surface air temperatures increasing by more than twice the global average.
Main recent changes affecting the oceans:
The global ocean has taken up more than 90% of excess heat in the climate system since 1970.
Since 1993, the rate of ocean warming has more than doubled.
The Southern Ocean accounted for ~40% of total heat gain in the upper 2000 m global ocean between 1970 and 2017.
Marine heatwaves doubled in frequency and were longer-lasting over the period 1982-2016.
The density stratification has increased in the upper 2000 m since 1970, due to ocean warming and freshwater addition.
The ocean has taken up 20-30% of the total anthropogenic CO2 emissions since the 1980s, leading to ocean acidification.
The ocean lost oxygen by 0.5-3.3% over the upper 1000 m between 1970 and 2010, mostly due to increasing ocean stratification, changing ventilation and biogeochemistry.
The Atlantic Meridional Overturning Circulation (AMOC) weakened between 2004 and 2017 compared to pre-industrial levels (1850-1900).
The total global mean sea-level (GMSL) rise between 1902 and 2015 amounts to 16 cm and the rate of GMSL rise between 2006 and 2015 is 3.6 mm per year (compared to 1.4 mm per year for the period 1901-1990). The 2 main contributions to GMSL rise are:
ice sheets and glaciers: 1.8 mm per year (0.77 mm for Greenland Ice Sheet, 0.61 mm for glaciers and 0.43 mm for Antarctic Ice Sheet)
ocean thermal expansion: 1.4 mm per year.
The GMSL rise has accelerated in the past years due to the increased ice loss from Greenland (doubling from 1997-2006 to 2007-2016) and Antarctic (tripling from 1997-2006 to 2007-2016) Ice Sheets. This sea-level rise is not spatially uniform, with regional differences of +/- 30% of GMSL rise, resulting from land ice loss and variations in ocean warming and circulation.
Model projections:
In order to make projections, climate models use different greenhouse gas concentration scenarios describing different climate futures, called representative concentration pathways (RCP). There are 4 different RCP scenarios, but the SROCC report mainly focuses on the lower-impact RCP2.6 and higher-impact RCP8.5. These results mainly come from the Coupled Model Intercomparison Project Phase 5 (CMIP5), used in the IPCC 5th Assessment Report (AR5) published in 2013.
Glacier mass loss between 2015 and 2100 = 18% (0.094 m sea-level rise) in RCP2.6 and 36% (0.2 m sea-level rise) in RCP8.5.
Greenland Ice Sheet contribution to sea-level rise between 2015 and 2100 = 0.07 m in RCP2.6 and 0.15 m in RCP8.5.
Antarctic Ice Sheet contribution to sea-level rise between 2015 and 2100 = 0.04 m in RCP2.6 and 0.12 m in RCP8.5.
Arctic autumn and spring snow cover decrease between 1986-2005 and 2031-2050 = 5-10%, followed by no loss in RCP2.6 and additional loss of 15-25% by 2100 in RCP8.5.
Permafrost area decrease by 2100 = 24% in RCP2.6 and 69% in RCP8.5.
Annual probability of Arctic sea-ice-free September by 2100 = 1% (once per century) for global warming of 1.5°C and 10-35% (1 to 3.5 events per decade) for global warming of 2°C.
Ocean heat uptake (top 2000 m) by 2100 = 2-4 times mores in RCP2.6 and 5-7 times mores in RCP8.5.
Ocean density stratification (top 2000 m, 60°S-60°N) increase from 1986-2005 to 2081-2100 = 1-9% in RCP2.6 and 12-30% in RCP8.5.
Ocean carbon uptake will increase, leading to higher ocean acidification.
Marine heatwave frequency increase = 20 times more in RCP2.6 and 50 times more in RCP8.5 (with largest increases in the Arctic and tropical regions). These marine heatwaves will also increase in duration, extent and intensity.
Extreme El Niño and La Niña events will increase in frequency and intensity.
The AMOC will weaken under all RCPs, although a collapse is unlikely.
GMSL rise between 1986-2005 and 2100 = 0.43 m in RCP2.6 and 0.84 m in RCP8.5 (the latter is higher by 0.1 m compared to the AR5 projections, due to an increased contribution from the Antarctic Ice Sheet). Rate of GMSL rise in 2100 = 4 mm per year in RCP2.6 and 15 mm per year in RCP8.5.
Increase in the frequency of extreme sea-level events, e.g. local sea-level events that occurred once per century are projected to occur at least once per year at most locations under all RCPs. This means that many low-lying megacities and small islands will experience historical centennial events at least annually by 2050 under all RCPs.
Wave height increase across Southern Ocean, tropical eastern Pacific and Baltic Sea, and decrease over North Atlantic and Mediterranean Sea.
Tropical cyclones: increase in the average intensity, increase in the proportion of the most intense ones (categories 4 and 5), increase in the average precipitation rates.
The SR15 report is a follow-up of the Paris Agreement adopted at the COP21 in December 2015. This report highlights the climate change impacts that could be avoided if limiting the increase in global temperature to 1.5°C vs. 2°C compared to pre-industrial levels (1850-1900). Some of the key messages of the SR15 are:
Human activities have now caused around 1°C of global warming above pre-industrial levels, and impacts on natural and human systems have already been observed (e.g. corals, fisheries, Arctic sea ice, coastal flooding, terrestrial ecosystems). This warming is 2-3 times larger in the Arctic compared to the global average.
Global warming will likely reach 1.5°C (above pre-industrial levels) before 2050 if the current pace of warming is maintained.
The maximum temperature reached is determined by both the cumulative net global anthropogenic CO2 emissions up to the time of net zero CO2 emissions and the level of non-CO2 radiative forcing in the decades prior to the time that maximum temperatures are reached.
The future climate change risks depend on the rate, peak and duration of warming. For example, the risks are larger if global warming exceeds 1.5°C before returning to 1.5°C by 2100, compared to a gradual stabilization to 1.5°C.
The projected climate change at 1.5°C and 2°C include (with larger change at 2°C compared to 1.5°C):
increase in mean temperature in most regions
increase in hot extremes in most inhabited regions (extreme hot days warm by up to 4°C at 2°C warming vs. 3°C at 1.5°C warming)
increase in heavy precipitation events in several regions
increase in the probability of drought in some regions
global mean sea-level rise (10 cm higher at 2°C compared to 1.5°C), with a rise well beyond 2100
Antarctic marine ice-sheet instability (MISI) and Greenland Ice Sheet irreversible loss could be triggered, leading to further sea-level rise
large losses in Arctic sea ice (the Arctic would be ice free in summer once per decade at 2°C warming, while it would be only once this century at 1.5°C)
loss of species (18% of insects, 16% of plants and 8% of vertebrates will lose more than 50% of their climatic range at 2°C, vs. 6% of insects, 8% of plants and 4% of vertebrates at 1.5°C)
permafrost thawing (1.5-2 million km2 higher loss in permafrost area at 2°C compared to 1.5°C)
coral reef loss (decline of more than 99% at 2°C compared to 70-90% at 1.5°C).
Emissions pathways:
to stay at 1.5°C: need to reduce global net anthropogenic CO2 emissions by ~45% between 2010 and 2030 and reach net zero around 2050
to stay at 2°C: need to reduce CO2 emissions by ~25% between 2010 and 2030 and reach net zero around 2070.
Our remaining carbon budget for limiting global warming to 1.5°C is 420 GtCO2 (66% probability) (using surface air temperature). Since our current rate of emissions is 42 GtCO2 per year, this remaining budget will be depleted in 10 years.
The current nationally stated mitigation ambitions under the Paris Agreement would lead to global greenhouse gas emission rates in 2030 of 52-58 GtCO2 per year. This is incompatible with the goal to stay below 1.5°C, which requires to reduce this emission rate below 35 GtCO2 per year in 2030. These nationally stated mitigation ambitions rather lead to a warming of 3°C by 2100.
Global model pathways limiting global warming to 1.5°C involve annual average investment in the energy system of ~2.4 trillion (= 2.4 x 1012) USD between 2016 and 2035, i.e. ~2.5% of the world GDP.