Future Regional Climate Change

 

The final section of Chapter 14 provides detailed regional climate change assessments.  Multi-model ensemble projections for mean surface air temperature and mean precipitation are principally assessed for each region.  Due to the large amount of material in this section, the projections for each region will be summarized only briefly in the form of bullet points.  Interested readers are referred to a series of table at the end of the chapter in the IPCC report for more information.  Table 14.1 presents a summary of regional averages for projected temperature and precipitation for three different periods in the 21st century relative to the 1986-2005 reference period.  Table 14.2 shows the assessed confidence in CMIP5 representations of regional scale present-day climate, major controlling climate phenomena, and future projections.  Table 14.3 summarizes the relevance of different climate phenomena for future regional climate change.  

 

Arctic

 

• It is likely that rising surface temperatures in the Arctic will be strongly linked to anthropogenic forcing that will dwarf contributions from natural variability from climate modes like NAO. 

• Warming will be enhanced to due polar amplification effects, such as albedo feedbacks.  Projections for 2100 under RCP4.5 (intermediate emissions scenario) indicate a winter temperature increase of 5 °C over land and 7 °C over the Arctic Ocean.

• It is likely that the Arctic region will see a significant increase in precipitation by 2050 due to enhanced precipitation associated with extratropical cyclones.

 

North America

 

• It is very likely that the anthropogenic warming signal in North America will dwarf that of natural variability by mid-century.  Warming in the winter is greatest in Alaska, Canada, and Greenland.

• Projected warming is associated with a projected two to four-fold increase in heat wave frequency over the course of the century.

• It is likely that precipitation in the northern half of North America will increase over the 21st century due to enhanced precipitation associated with extratropical cyclones (Fig. 14.18).

• CMIP5 models do not consistently show a precipitation decrease in the southwestern U.S., in contrast to previous model iterations.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Central America and Caribbean

 

• It is likely that warm season precipitation will decrease in the Caribbean region in the 21st century.  There is only medium confidence that Central America will also experience a precipitation decrease over this time period.

• Mid-century warming in this region is expected to be 2-3 °C, with the greatest warming occurring in the summer months. 

 

South America

 

• It is very likely that temperatures will increase across the entire South American continent, with the greatest warming focused in southern Amazonia.

• It is very likely that precipitation during the rainy season (DJF) will increase in southeastern and northwestern South America and decrease in already arid central Chile (Fig. 14.21a).  It is very likely that less rainfall will occur in eastern Amazonia during the dry season (JJA) (Fig. 14.21b).

• There is high confidence in a projected increase in precipitation extremes in this region.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Europe and Mediterranean

 

• There is high confidence in model projections of mean temperature in this region.  It is very likely that temperatures will continue to increase across the entire region during the 21st century. 

• The length, intensity, and frequency of heat waves are very likely to increase in the region.

• There is medium confidence that precipitation will increase in Europe (annual mean) and decrease in the Mediterranean region (summer mean).

 

Africa

 

• It is very likely that all of Africa will continue to warm during the 21st century.

• The already arid Sahara region is projected to remain very dry (very likely).

• Rainfall is likely to increase in Eastern Africa during the short rainy season, but there is low confidence in precipitation changes the rest of the year.

 

Central and North Asia

 

• All areas are projected to warm, with a stronger than global mean increase in northern Asia.

• Precipitation is projected to increase in both northern Asia (very likely) and central Asia (likely).  Extreme precipitation events are likely to increase in both regions.

 

East Asia

 

• There is medium confidence that summer precipitation in East Asia will increase, due to an intensified East Asian monsoon.

• Regional warming is expected to be above the global mean in East Asia.

• Extreme winds and rainfall associated with tropical cyclones are likely to increase.

 

West Asia

 

• It is very likely that temperatures will continue to increase in this region, though models still have a difficult time simulating climate well in this region.

• There is medium confidence that there will be an overall reduction of precipitation in this region.

 

South Asia

 

• There is high confidence in the projected rise in temperature in South Asia.

• Summer monsoon precipitation is projected to increase in this region (medium confidence).

 

Southeast Asia

 

• Warming is very likely to continue, but projections exhibit significant sub-regional variations.

• A moderate increase in rainfall is projected for this region (medium confidence).

 

Australia and New Zealand

 

• It is very likely that temperatures will continue to rise in both Australia and New Zealand, occurring at a rate similar to the global mean for the former and less than the global mean for the latter (due to buffering effect of surrounding oceans).

• The frequency of very warm days is very likely to increase in Australia in this century.

• Flood and drought occurrence is expected to double in New Zealand during the 21st century.

 

Pacific Islands

 

• It is very likely that warming will continue in this region during this century.  An increase is also expected for the frequency and magnitude of extreme high temperatures.

• Rainfall is likely to increase, but models remain somewhat uncertain on this projection due to effects of regional climate phenomena.

 

Antarctica

 

• It is very likely that Antarctic temperatures will continue to rise over the course of the 21st century, but at a rate less than that of the global mean. 

• It is likely that precipitation will increase as temperatures rise, up to 20% in East Antarctica (medium confidence).