U.S. Releases 4th National Climate Assessment

U.S. Releases 4th National Climate Assessment

December 12, 2018 0 By ThielWx

On Friday November 24th, while many were recovering from Thanksgiving, Black Friday, or both, the Released the 4th National Climate Assessment (NCA4) was delivered to the White House and Congress. While the event was in some degree politicized by its timing and the current state of the US “political climate”, the information contained in the report is what truly matters.

So…what is the ‘National Climate Assessment’?

I’m glad you asked hypothetical reader!

Beginning in the 1990s, a federal program called the U.S. Global Change Research Program, lead by NOAA, has been tasked with delivering a climate report to the US government every four years. The objectives of the report are to evaluate the current state of Earth’s climate and it’s impacts on the United States, along with climate projections for the next 25 to 100 years and their subsequent impacts.

Over 300 federal and non-federal experts volunteered their time to write the report, with an additional 1000 individuals across the country were able to provide feedback throughout its creation. Following this, 13 federal agencies gave input, with a final external review by the committee of the National Academies of Sciences, Engineering, and Medicine.

The result of all of this? A 1,513 page document that serves as a complete resource for policy decisions at the federal, state, and local levels. As the Earth’s climate evolves, the NCA4 provides projected impacts under various climate scenarios, and the effectiveness of mitigation strategies for 10 regions of the United States, and 18 national topics.

State of the Climate

As mentioned, this report is massive (even the abridged version is 196 pages in length), so we will only focus on the key messages from a select few chapters. The first we’ll discuss is to promote a general understanding of how our climate is evolving due to human activity. Global average temperatures have increased by 1.8°F since 1901, which compared to natural variability/cycles is insanely fast. To get it out of the way now, it has been consistently proven that human activity, mostly through the release of carbon dioxide, is the disproportionate driver of these changes in the past 100 years, and will continue to accelerate this warming trend into the future.

A time series plot of carbon dioxide concentrations (measured and proxy data) over the past 40,000 years. The key attribute to notice is the rate of increase over the past 50 years, which is unprecedented in magnitude. Source

“With significant reductions in emissions, global temperature increase could be limited to 3.6°F (2°C) or less compared to preindustrial temperatures. Without significant reductions, annual average global temperatures could increase by 9°F (5°C) or more by the end of this century compared to preindustrial temperatures.”

U.S. Global Change Research Program – 4th National Climate Assessment

While an increase in temperatures has often been the standard for monitoring the changes in climate. The cascading effects on sea levels, severe weather, and numerous other systems will present new challenges on the United States economy, health, and security.

Carbon emissions projections, and their associated temperature changes through 2100. The spread of the projections show different scenarios, with RCP2.6 showing an aggressive carbon emissions reduction scenario resulting in 2.6°F of warming, up to RCP8.5 as the “business as usual” scenario, with 8.5°F of warming. Source (Page 91)
Sea Levels

The report states that global sea levels have risen by 8 inches since 1900. While this amount may not appear significant, what is truly alarming is that over half of this increase has occurred since 1993. Increasing sea levels present a large threat to coastal cities and communities, increasing the likelihood of coastal flooding from events such as high tide events (also known as King Tides) and storm surge from tropical cyclones.

Relative to the year 2000, sea level is very likely to rise 1 to 4 feet (0.3 to 1.3 m) by the end of the century. Emerging science regarding Antarctic ice sheet stability suggests that, for higher scenarios, a rise exceeding 8 feet (2.4 m) by 2100 is physically possible, although the probability of such an extreme outcome cannot currently be assessed.

U.S. Global Change Research Program – 4th National Climate Assessment
Severe Weather

Warming global temperatures have also had an impact on atmospheric dynamics. One of the biggest consequences is that the atmosphere is able to “hold” more water, resulting in greater precipitation extremes such as flooding events, extended periods of drought, and tropical activity such as “atmospheric rivers”.

In the future, Atlantic and eastern North Pacific hurricane rainfall and intensity are projected to increase, as are the frequency and severity of landfalling “atmospheric rivers” on the West Coast.

U.S. Global Change Research Program – 4th National Climate Assessment

The Future: Emissions Mitigation and Adaptation

With the future impact our climate will have on not just severe events, but also human health, the US economy, and security both foreign and domestic, mitigating and abating these effects will provide numerous benefits. A key point to make is that mitigation and adaptation go hand in hand, and having both can lead to numerous positive economic and societal benefits. In short, this means that we cannot assume the “all hope is lost” mentality. 

Proactive adaptation initiatives—including changes to policies, business operations, capital investments, and other steps—yield benefits in excess of their costs in the near term, as well as over the long term.

U.S. Global Change Research Program – 4th National Climate Assessment

The good news is that climate adaptation and mitigation has gained traction in some crucial areas as of recent, including planners, builders, engineers, architects, contractors, developers, and more. So what does this mean?

It means that individuals are not only considering Earth’s current climate, but also Earth’s future climate and associated impacts. And if we can continue to reduce our collective carbon footprint, then the US alone looks to save billions of dollars annually. When comparing the impacts of warming by 4.5°F with 8.5°F, the annual savings are staggering (see figure below).

Under scenarios with high emissions and limited or no adaptation, annual losses in some sectors are estimated to grow to hundreds of billions of dollars by the end of the century. It is very likely that some physical and ecological impacts will be irreversible for thousands of years, while others will be permanent.

U.S. Global Change Research Program – 4th National Climate Assessment
Each color of the pie chart correlates with the estimated economic losses in the table, with the percentage saved under the 4.5°F warming scenario compared to the 8.5°F warming scenario.  Figure Source Here

To quickly summarize, please know that climate change is a fundamental issue as we continue into the 21st century, with fundamental solutions that will pay dividends in the long-term. The 4th National Climate Assessment goes into exponentially more detail than I have, with calculated climate projections and impacts down to the regional level, so I definitely encourage you check out the links below to become more climate-aware!

Resources, references, and helpful links: