The Intergovernmental Panel on Climate Change (IPCC) recently released its Climate Science 2021 Report, which summarizes the latest global research on the physical drivers behind climate change and the resulting impacts that are likely to occur. The research summarized in the report adds to our knowledge on climate change and provides more detail on what the future may hold. Read on to learn more about some of the IPCC’s key findings!

1. The impact of human activities on the climate is unequivocal.

Observations have unequivocally shown that human activity, especially the burning of fossil fuels, has led to an increase in atmospheric greenhouse gas (GHG) concentrations. This increase is driving a range of changes to the global climate, including warming surface temperatures and changes in precipitation. Comparing the last decade (2010 – 2019) to the period 1850 – 1900, it is likely that human activity has increased the Earth’s temperature by approximately 2°F (1.1°C). Human activity is also the likely driver behind increasing global precipitation (as well as increases in drought), decreasing sea ice and retreating glaciers, ocean warming, and sea level rise.

2. The rate and scale of recent changes across the climate system are unprecedented when compared to the past.

Carbon dioxide (CO2) concentrations are higher than at any time in the last two million years, and concentrations of methane (CH4) and nitrous oxide (N2O) are higher than the last 800,000 years. Global surface temperatures have increased faster in recent decades than over the last 2,000 years, and temperatures over the last decade (2010 – 2019) were warmer than any long-term trends over the last 125,000 years. The global mean sea level has risen faster over the last century than any preceding century over the last 3,000 years.

3. Human-induced climate change is leading to weather and climate extremes across the globe.

Warmer weather extremes, including heatwaves, are becoming more frequent and more intense while cold weather extremes are becoming less common. Heavy precipitation events are also becoming more frequent and more intense in many places while at the same time, the occurrence of droughts has also increased due to increased soil moisture loss. Fire weather has increased in some regions of all inhabited continents. The proportion of major tropical cyclones (classified as Category 3 – 5) occurring each season has also increased over the last several decades, as has the amount of precipitation associated with cyclones.

4. A doubling of atmospheric carbon dioxide will lead to a 5.4°F (3°C) increase in global average surface temperature.

The IPCC’s estimate of the likely range for the increase in global average surface temperature is 3.6°F to 7.2°F. These estimates have been updated based on a better understanding of climate processes, more evidence about past climate trends, and improved modeling.

5. Global surface temperatures will continue to increase unless deep cuts are made to GHG emissions in the coming decades.

By the end of the century, global temperatures are likely to be 1.8°F to 3.2°F higher than the 1850 – 1900 baseline under the IPCC’s very low emissions scenario. Under a very high GHG emissions scenario, temperatures could be as much as 5.9°F to 10.6°F higher than baseline. For comparison, temperatures have not been sustained at 4.5°F or more above the 1850 – 1900 baseline for the last 3 million years!

6. As surface temperatures increase, the accompanying changes in the climate system are likely to become larger.

With every incremental rise in global surface temperature, changes in the climate system continue to become larger. These changes include more frequent and more intense heat waves, heavy precipitation events, and drought, as well as an increase in the proportion of major tropical cyclones. Other changes that are likely to increase in severity include the loss of Arctic sea ice, snow cover, and permafrost.

7. Many of these changes to our climate system are likely irreversible over timescales of centuries or longer, especially changes to ice sheets and rising global sea levels.

Past GHG emissions (since 1750) have already locked in climate change for several centuries into the future. Ocean warming and melting glaciers and polar ice caps are likely to continue for the remainder of the 21st century and possible longer. Sea levels are likely to keep rising for several centuries, although the rate of rise will likely taper off depending on the degree to which we can limit future GHG emissions and the accompanying rise in temperatures.

What Can Be Done About Climate Change?

There are two broad sets of strategies to combat climate change. First, we can take action to lower GHG emissions and slow down human-induced warming. This is essential to avoid the worst effects of climate change. However, even with efforts to limit GHG emissions, the IPCC report describes several changes that are likely to occur over the next several decades to centuries. Therefore, the second strategy is to adapt to these challenge s by increasing the resiliency of our food and water supplies, our cities, and our infrastructure, while also taking steps to minimize GHG emissions.

According to the IPCC, minimizing the risk of catastrophic climate change requires a rapid reduction in CO2 emissions and reaching at least net zero CO2 emissions. Energy is one of the biggest sources of GHG emissions, and technologies such as renewable energy, electric vehicles, nuclear power, and hydrogen will likely play a vital role. In addition, sustained reductions in methane (CH4) emissions would help reduce global warming and also improve air quality.

The IPCC report also considers the effects of carbon dioxide removal (CDR), which involves using technology to remove CO2 from the atmosphere. At least in theory, it is possible to achieve net negative carbon emissions by using carbon capture technologies to remove CO2 from the atmosphere. Several pilot and prototype CDR projects have been announced, but this approach has yet to be implemented at scale. CDR is different from carbon capture and sequestration (CCS), although there are some similarities between the two. CCS focuses on capturing CO2 from high-concentration streams such as exhaust gases from power plants, while CDR aims to remove atmospheric CO2 at ambient concentrations. However, in both cases, the captured or removed CO2 would need to be sequestered belowground or converted into other products that would lock it away and prevent it from being re-emitted into the atmosphere.

Potomac-Hudson Engineering, Inc. (PHE) has been providing environmental consulting services to government and private sector clients for over 30 years. Our expertise includes environmental planning and analysis and environmental compliance, with a focus on greenhouse gas emissions and climate change. We have conducted lifecycle greenhouse gas emissions and climate change impact analyses for large and small infrastructure projects, including CCS projects, power plants, pipelines, and others. To learn more about how PHE can help you reduce your GHG emissions, improve your sustainability posture, and prepare to respond to the challenges posed by climate change, contact Samir Qadir, Senior Engineer, at samir.qadir@phe.com.

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