In my previous post I reported on the 4th National Climate Assessment, Volume 1. That volume deals with the natural science findings. Volume 2 deals with how climate change is projected to impact the United States, and with mitigation and adaptation. Unlike reports by the IPCC, the National Climate Assessment focuses on the United States. As with all of the IPCC and NCA reports, the 4th National Climate Assessment is far too large and substantive to fully summarize in a brief blog post. What follows is a selection of a few of the findings.

Figure 1. Source: US Global Change Research Program, 2018.

Figure 1 projects U.S. economic damage from climate change in 2090 under the low emission scenario (RCP 4.5) and the high emission scenario (8.5). The intangibles that make life worth living, what we call quality of life, are not easy to put a dollar value on, and this chart does not address them.

In the chart, the columns represent various sectors of the economy. The blue portion represents the damages under RCP 4.5, while the whole column represents the damages under RCP 8.5 Thus, the orange portion represents the difference between the two. The largest economic damages come from 3 sectors: Labor, Extreme Temperature Mortality, and Coastal Property. In addition, in most of the sectors, the damages under RCP 8.5 are more than twice the damages under RCP 4.5.

(Click on chart for larger view.)

Figure 2. Source: U.S. Global Change Research Program, 2018.

Figure 2 shows projected carbon emissions, temperature change, and U.S. economic damage from climate change under various emission scenarios. The left side of the chart shows that observed carbon emissions are following the high scenario, and there is no evidence that they are suddenly about to revert to the low emission scenario. The right side shows that the high emissions scenarios lead to larger increases in temperature and correspondingly larger damages to the U.S. economy.

The Overview of the report summarizes some of the specific risks the USA faces from climate change. It is quite a list, but it puts real form to projections that often are statistical or vague. To paraphrase:

• Rising sea levels, higher storm surges, and increased high tide flooding will impact coastal infrastructure, damaging electrical and natural gas supply lines, and causing problems with access to goods from overseas. About $1 trillion in coastal property will be impacted. Coastal cities will experience daily flooding.
• Wildfire in the West will increase, damaging ranches and rangelands; increasingly it will damage property in cities and take human lives. Energy transmission and production will be damaged.
• Thawing permafrost in Alaska will damage roads and buildings, including oil and gas operations. This will be partially offset by a longer ice-free season.
• Yields of major U.S. crops (corn, soybeans, wheat, rice, sorghum, and cotton) are expected to decline due to higher temperatures and changes in water availability, disease, and pests. These will percolate through the economy, resulting in less availability of agricultural products, and increased prices.
• Human productivity equal to almost 2 billion labor hours is expected to be lost annually due to extreme temperatures, resulting in an estimated $160 billion in lost wages. States in the Southeast and Southern Great Plains are expected to be impacted hardest.
• Fresh water quality and quantity are threatened by rising temperatures, reduced mountain snowpack, sea level rise, saltwater intrusion, drought, flooding, and algal blooms. In some places, the availability of safe and dependable water will be threatened.
• Hydropower supplies are expected to decrease as a result of changes in mountain snowpack.
• Drought will impact oil and gas drilling and refining, all of which use water intensely.
• Tourism will be impacted by changes in snowpack and wildfire. Communities dependent on tourism will be impacted.
• Air quality will be impacted by higher temperature, higher humidity, and increased smoke from wildfires. Reduced air quality is expected to adversely impact human health.
• Species already are, and will continue, to shift their growing ranges and growing seasons in response to climate change. Mismatches between species and the availability of the resources they need to survive are expected to occur. Extinctions and transformative impacts on some ecosystems are expected.
• Heavy-to-severe coral bleaching is expected to onset across most of the Hawaiian Islands, Guam, and American Samoa by the late 2030s. This will impact fisheries yields and tourism. (Paradise Lost – where’s John Milton when you need him?)
• Rising temperatures are expected to increase illness and death (especially among older adults, pregnant women, and children), partially (but only partially) offset by a reduction in cold-weather deaths.
• Rising temperatures are expected to reduce electricity generation capacity while simultaneously increasing demand for it and its costs. Power outages and blackouts are expected to increase, and household budgets will be strained. Marginal populations and the economically disadvantaged will be impacted even more severely.
• Rising temperatures are expected to threaten human health by promoting the growth of foodborne and waterborne pathogens. Diseases like Lyme disease, West Nile, chikungunya, dengue, and Zika are expected to spread and become more common.
• Every armed service (but especially the Navy, Marines, and Coast Guard), has many bases located in coastal regions. They are expected to be threatened by climate change, and in some cases made unusable. Many of the transportation routes between these bases are similarly located in coastal regions and may become unusable. Thus, climate change is expected to become a significant challenge to the national security apparatus of this country.
• All of the above expected effects of climate change are expected to cause increased stress, leading to increased rates of stress-related diseases, including mental illness.

In terms of mitigation and adaptation, the report states that power sector emissions were 25% below 2005 levels in 2016, the largest emissions reduction for a sector of the American economy over this time. This decline was in large part due to increases in natural gas and renewable energy generation, as well as enhanced energy efficiency standards and programs. Under continued business-as-usual projections, U.S. carbon dioxide and other greenhouse gas emissions show flat or declining trajectories over the next decade with a central estimate of about 15% to 20% reduction below 2005 levels by 2025. (While it is great that U.S. emission have declined, worldwide emissions continue to increase.)

Figure 3: Mitigation Policies by State and Type. Source: U.S. Global Change Research Program.

The report notes that efforts to adapt to climate change and to mitigate its effects have increased across the country, but are not even close to adequate. Adaptation is an issue for local planning, as it must take into account both the specific damages anticipated in the locale and many local characteristics such as topography, local water supply, etc. Mitigation follows pathways that are more common across different locations. Figure 3 shows is a map showing the number of GHG mitigation policies in place in each state, by type of policy.

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Figure 1. Source: U.S. Energy Information Agency.

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The fact that Missouri has mitigation policies in place does not necessarily mean that GHG emissions have substantially decreased. I last reported on state GHG emissions using data from 2013. At that time, Missouri’s GHG emissions from fossil fuel were still above their level in 2000. Figure 4 republishes a chart from that post showing GHG emissions over time from Missouri and some neighboring states.

The document contains a great deal more than I can report in this post. Those who are interested can follow the link in the Sources section below to the original document. The whole document is available as a single download, or you can download individual chapters.

Sources

USGCRP, 2018: Impacts, Risks, and Adaptation in the United States: Fourth National Climate Assessment, Volume II [Reidmiller, D.R., C.W. Avery, D.R. Easterling, K.E. Kunkel, K.L.M. Lewis, T.K. Maycock, and B.C. Stewart (eds.)]. U.S. Global Change Research Program, Washington, DC, USA, 1515 pp. doi: 10.7930/NCA4.2018. Downloaded 12/5/2018 from https://nca2018.globalchange.gov.