The IPCC Report and “The Physics of Climate Change”
The newest Intergovernmental Panel on Climate Change’s (IPCC) Sixth Assessment Report released in late February paints a bleak picture of the global and local effects of climate change in coming decades, and of the challenges that governments and citizens face as they work to address the problems that will arise due to human induced global warming.
Have things changed dramatically since I published “The Physics of Climate Change” last year at this time? Not really. Just a clearer sense of current issues, and a clearer statement of what needs to be done and the challenge of doing it.
The key points are pretty clear.
(1) We are dumping about 10 billion tons of carbon into the atmosphere each year, about 50% of which will remain there for a millennium. In 1900 there were about 600 billion tons of carbon in the atmosphere. Now there are about 840 billion tons. In order to keep the global temperature below about 1.5 degrees Celsius above the 1900 value we have to keep the atmospheric concentration below about 900 billion tons. The difference is about 12 years at current rates of emission. This underscores the urgency of addressing climate change. It is not as if the effects will be near term. However, the challenge of staving off the effects gets harder with every year we continue to dump carbon into the atmosphere at current levels.
(2) Much of sea level rise is already written in stone, given the heat already dumped in the ocean. We are guaranteed to have a minimum of about 30 centimeters of sea level rise this century, which is enough to cause significant damage in many coastal areas. Greenland’s ice sheet is melting at an accelerating rate. The tipping point value of temperature rise, beyond which its complete disappearance (over the course of centuries) is uncertain. It could be as high as 7 degrees Celsius, or as low as 1.5-2 degree Celsius. The loss of Greenland’s ice sheet would raise sea levels by 7 meters. This has happened several times in the past.
(3) Oceans are already being affected in other ways. Dissolved CO2 is making the oceans more acidic and increased temperatures are lowering the oxygen content. Since 1950, oxygen content in the oceans has dropped by over 2%.
(4) The effects of global warming will be unevenly spread over the globe. In equatorial areas, the signal from human induced global warming can already be disentangled from noise on a seasonal basis. By the end of the century in these regions the average summer temperature will exceed the warmest summer thus far 100% of the time. Some regions will become effectively impossible for human habitation. The effects of climate change on agriculture are also already evident in areas including South and Central America, and parts of Africa. Many areas will become drier and hotter, and will need new technologies to continue to produce adequate food.
The report stresses an issue I also stressed at the end of my book: There is time to adapt to and mediate—with foresight—some of the effects of climate change in many areas at risk in the near term with new technologies. However, the new report also points out that some areas have already reached a level where adaptation cannot head off significant damage.
The importance of addressing developing nations’ needs for improved infrastructure, clean water, and power are also explicitly discussed in the new report. These needs will require energy intensive sources, as well as economic development, both of which will result in increased greenhouse gas emissions from those regions, but there are currently no real alternatives to this path.
The main conclusions of the IPCC report are these:
(1) Climate change is already causing disruption in every region in the world with just 1.1 degrees C of warming.
(2) Greenhouse gases already in the atmosphere and current trends will make significant climate impacts inevitable in the near term. In the next decade climate change could drive 32-132 million more people into extreme poverty.
(3) With just 1.5 degrees C of global warming, many glaciers around the world will either disappear completely or lose most of their mass; an additional 350 million people will experience water scarcity by 2030; and as much as 14% of terrestrial species will face high risks of extinction.
(4) Adaptation needs will reach $127 billion and $295 billion per year for developing countries alone by 2030 and 2050, respectively.
(5) Existing adaptation options can reduce climate risks if they’re sufficiently funded and implemented more quickly.
(6) Certain regions of the world are already experiencing changes at the limit of adaptation, where climate impacts are so severe that no existing adaptation measures can effectively prevent losses. These impacts include loss of coral reef ecosystems, and existing sea level rise in low-lying areas. With 2 degrees of warming, water shortages and crop failures will result in many areas to which these regions cannot adapt.
(7) The window for effective action to head off worst effects is quickly closing.
The world is not ending, but we need to have a clear picture of what we can do, and what, at a minimum, we need to do it in order to stave off the worst impacts of climate change. Climate change is already occurring, with real consequences.
The world has to concertedly address the following question, and it has to start to do so now: How can we globally work to build infrastructure, for developing nations in particular, to protect those most at risk now from the impacts of climate change, and encourage sufficient innovation to effectively reduce carbon emissions? This presents both technological and political challenges.
If the present is any guide, the technological challenges are dwarfed by the political ones.