It is usually impossible to connect specific weather events to global warming. Instead, global warming is expected to cause changes in the overall distribution and intensity of events, such as changes to the frequency and intensity of heavy precipitation. Broader effects are expected to include glacial retreat, Arctic shrinkage including long-term shrinkage of the Greenland ice sheet, and worldwide sea level rise. Some effects on both the natural environment and human life are, at least in part, already being attributed to global warming. A 2001 report by the IPCC suggests that glacier retreat, ice shelf disruption such as that of the Larsen Ice Shelf, sea level rise, changes in rainfall patterns, and increased intensity and frequency of extreme weather events are attributable in part to global warming.Other expected effects include water scarcity in some regions and increased precipitation in others, changes in mountain snowpack, and some adverse health effects from warmer temperatures.

Social and economic effects of global warming may be exacerbated by growing population densities in affected areas. Temperate regions are projected to experience fewer cold-related deaths but many more deaths from heat exposure. A summary of probable effects and recent understanding can be found in the report made for the IPCC Third Assessment Report by Working Group II. The newer IPCC Fourth Assessment Report summary reports that there is observational evidence for an increase in intense tropical cyclone activity in the North Atlantic Ocean since about 1970, in correlation with the increase in sea surface temperature (see Atlantic Multidecadal Oscillation), but that the detection of long-term trends is complicated by the quality of records prior to routine satellite observations. The summary also states that there is no clear trend in the annual worldwide number of tropical cyclones.

Additional expected effects include sea level rise of 0.18 to 0.59 meters (0.59 to 1.9 ft) in 2090–2100 relative to 1980–1999,^[2] new trade routes resulting from arctic shrinkage,^[66] possible thermohaline circulation slowing, increasingly intense, in some locations, (but less frequent) hurricanes ^[67]and extreme weather events,^[68] reductions in the ozone layer, changes in agriculture yields, changes in the range of climate-dependent disease vectors,^[69] which have been linked to increases in the prevalence of malaria and dengue fever,^[70] and ocean oxygen depletion.^[71] Increased atmospheric CO₂ increases the amount of CO₂ dissolved in the oceans.^[72] CO₂ dissolved in the ocean reacts with water to form carbonic acid, resulting in ocean acidification. Ocean surface pH is estimated to have decreased from 8.25 near the beginning of the industrial era to 8.14 by 2004,^[73] and is projected to decrease by a further 0.14 to 0.5 units by 2100 as the ocean absorbs more CO₂.^[2][74] Heat and carbon dioxide trapped in the oceans may still take hundreds of years to be re-emitted, even after greenhouse gas emissions are eventually reduced.^[7] Since organisms and ecosystems are adapted to a narrow range of pH, this raises extinction concerns and disruptions in food webs.^[75] One study predicts 18% to 35% of a sample of 1,103 animal and plant species would be extinct by 2050, based on future climate projections.^[76] However, few mechanistic studies have documented extinctions due to recent climate change,^[77] and one study suggests that projected rates of extinction are uncertain.^[78]