The IPCC 6th Assessment provides a striking range of potential futures, depending primarily on the choices people make over the coming decades with respect to CO2 emissions. In the lowest emission scenarios (SSP1-1.9 and SSP1-2.6), emissions fall immediately and rapidly, CO2 stabilizes, and climate remains relatively constant in the future with warming of less than 2 C above preindustrial levels. We might call this the “new normal.” On the other hand, at high levels of emissions (SSP3-7.0 and SSP4-8.5), CO2 and warming continue to increase, and simulated impacts are severe. Warming is most severe on land, in continental interiors, and in the Arctic with average temperatures 5 C warmer than preindustrial by 2100. Large parts of the subtropical continents become very dry both through reduced rainfall and the increased evaporative demand of warmer air. Depletion of soil moisture is especially severe over the Mediterranean region, the Amazon Basin, and the southwestern USA. Both extremely hot days and extremely heavy rainfall become dramatically more frequent. In high CO2 emission scenarios, carbon sinks on land and in the ocean absorb a smaller fraction of emissions due to extreme warming. Arctic summer sea ice is lost completely by late century in all but the lowest emission scenarios. Sea levels continue to rise in all scenarios and accelerate in later centuries under high emissions.
Upon completion of this module you should be able to:
- Explain the dependence of the magnitude of future warming on emissions.
- Outline geographic patterns in expected precipitation changes and explain physical mechanisms that explain them.
- Describe how temperature changes impact vapor pressure, water holding capacity, and heavy rainfall.
- Explain how drought integrates changes in both precipitation and water demand.
- Assess how rising sea levels impact the frequency of coastal flooding.
Slide Deck / Lecture
- Over the next several decades, where in the world do we expect much more warming that the global average and why
- Under a low-emission scenario like RCP2.6, how much additional warming should we expect in North America by 2100 compared to today?
- As the global average temperature rises, what will happen to the global average rate of precipitation?
- As the global average temperature rises, which regions will likely receive more rainfall? Which regions will likely receive less rainfall?
- In addition to changes in rainfall, how does a warmer climate generally lead to much drier soils?
- Over what regions is food production likely to decrease due to global warming?
- By the year 2100, how much is global mean temperature is likely to increase above preindustrial conditions in the RCP8.5 scenario? In that case how much warming would the middle of North America experience?
- Describe three mechanisms by which warmer climates promote increases in wildfire in our region.
- Explain how rising seas impact coastal communities many decades before they are permanently inundated.
- Why is it much more difficult to project sea levels than global mean temperature? Why might sea levels continue to rise for many centuries after warming stabilizes?