Synthesis Report Contents of the report SYR 6 6

Synthesis Report
Contents of the report SYR 6 6.2
6.2 Driving Factors and Estimates of Future Climate Change and Its Implications
Correct discovery
Following current climate change mitigation policies and related sustainable development practices, global greenhouse gas emissions will continue to grow in the coming decades. {WGIII 3.2 , SPM }

For the next two decades, a series of SRES emissions scenarios predict a temperature increase of about 0.2 ° C per decade. {WGI 10.3 , 10.7 , SPM }

Continued emission of greenhouse gases at or above the current rate will lead to further warming and trigger many changes in the global climate system of the 21st century that will likely be larger than those observed during the 20th century. {WGI 10.3 , 11.1 , SPM }

The same pattern of future warming can be seen in all scenarios, ie the warming of the land is greater than that of the adjacent sea and warming is more pronounced in the high latitudes of the northern hemisphere. {WGI 10.3 , 11.1 , SPM }

Warming tends to reduce the uptake of atmospheric carbon dioxide by terrestrial ecosystems and the oceans, thereby increasing the anthropogenic emissions remaining in the atmosphere. {WGI 7.3 , 10.4 , 10.5 , SPM }

Due to the time scales associated with various climatic processes and feedback, anthropogenic warming and sea-level rise can persist for centuries even with a significant reduction in greenhouse gas emissions to stabilize greenhouse gas concentrations. {WGI 10.7 , SPM }

It is very unlikely that equilibrium climate sensitivity will be less than 1.5 ° C. {WGI 8.6 , 9.6 , Box 10.2 , SPM }

Some systems, industries and regions may be particularly affected by climate change. These systems and industries include ecosystems (tundra, northern forests, mountains, Mediterranean ecosystems, mangroves, salt marshes, coral reefs and sea ice biomes), low-lying coastal zones, some mid-latitudes arid and tropical arid regions Resources, areas that depend on melting ice and snow, agriculture in low latitudes, and human health in areas of low resilience. These include the Arctic, Africa, small islands and the Greater Delta of Asia and Africa. In other areas, even in high-income areas, some populations, areas and activities are especially at risk. {WGII TS.4.5 }

The impact is likely to increase due to the increased frequency and intensity of some extreme weather events. Recent events have confirmed the vulnerability of some industries and regions to heat waves, tropical cyclones, floods and droughts, including in developed countries. This provides stronger reasons for concern than the findings of the Third Assessment Report. {WGII Table SPM.2, 19.3}

The key uncertainty
Uncertainty about balancing climate sensitivity leads to uncertainty about projected warming under a given carbon dioxide equivalent stability scenario, and the uncertainty of carbon cycle feedback leads to emissions trajectories required to reach a certain level of stability Uncertainty. {WGI 7.3 , 10.4 , 10.5 , SPM }

Estimates of the different feedback strengths of the climate system vary widely across models, notably cloud feedback, ocean heat uptake, and carbon cycle feedback, although progress has been made in these areas. In addition, the confidence of some variables (such as temperature) is greater than that of other variables (such as precipitation), and the confidence of larger spatial scales and longer time averages is also higher. {WGI 7.3 , 8.1 – 8.7 , 9.6 , 10.2 , 10.7 , SPM ; WGII 4.4 }

The impact of aerosol on the magnitude of temperature response, cloud and precipitation remains uncertain. {WGI 2.9 , 7.5 , 9.2 , 9.4 , 9.5 }

Future changes in ice formations in Greenland and Antarctic ice sheets, particularly as a result of changes in ice flow, are a major contributor to the increased uncertainty in the estimation of sea level rise. The uncertainty of the infiltration of heat into the oceans also contributed to the uncertainty of rising sea levels in the future. {WGI 4.6 , 6.4 , 10.3 , 10.7 , SPM }

Large-scale changes in the ocean circulation after the 21st century can not yet be reliably assessed due to the uncertainty of the Greenland ice sheet recharge and the mode of response to warming. {WGI 6.4 , 8.7 , 10.3 }

Estimates of climate change and its effects after about 2050 depend heavily on scenarios and patterns. Improving projections requires raising awareness of sources of uncertainty and strengthening systematic observation networks. {WGII TS.6 }

Impact studies are constrained by the uncertainty of regional climate change, especially rainfall projections. {WGII TS.6 }

Knowledge of events with low probability / impact and cumulative impact of smaller events is often limited, but this is exactly what is needed for risk decision making.