| Effect | IPCC Likelihood | % Probability, Confidence |
| 20-30% of plant and animal species become extinct if global average temperatures exceed 2.7-4.5°F (1.5-2.5°C) | Likely (extinction rate) Medium confidence temperatures will exceed 2.7-4.5°F (1.5-2.5°C) | >66% 5 out of 10 chance |
| By 2080, millions experience floods due to sea-level rise | Very high confidence | At least 9 out of 10 chance |
| Frequency of warm spells and heat waves increases | Very Likely | >90% |
| Frequency of heavy precipitation increases | Very likely | >90% |
| Areas affected by drought increase | Likely | >66% |
| Intense tropical cyclone activity increases | Likely | >66% |
| Millions experience adverse health effects, especially in undeveloped countries | Likely | >66% |
Impacts from higher temperatures are difficult to evaluate, since they depend not only on how warm things get, but also on how fast humans adapt. This, in turn, depends on such things as national wealth and access to education and health care. This table describes impacts that the experts are reasonably confident about.