Thoughts From Engineers: Climate Report Issues Bleak Predictions
The Intergovernmental Panel on Climate Change (IPCC) released the “Sixth Assessment Report” on the quantifiable science behind climate change on Aug. 7, 2021. Sponsored by the United Nations (UN), the report (found at bit.ly/3l4L4jQ) represents the collective effort of more than 200 climate scientists from around the globe who have used advanced analytical tools and complex models to develop the most-current assessment along with future projections.
Since the report’s initial publication in 1990, the assessment is widely viewed as the definitive authority on the topic of climate change. As the work product of numerous climate experts, the analysis is weighty and substantial. The technical document alone is nearly 500 pages in length. For those of us looking for a quicker read, the “Executive Summary” hits the main points.
The report’s findings are not ambivalent. In fact, the IPCC report is a veritable “bullet between the eyes” in its raw analysis of the state of Earth’s climate. Here are just two of the report’s many unsettling conclusions:
1. Levels of CO2 were recorded as being higher in 2019 that at any other time in the last 2 million years.
2. Evidence of change in extremes in the form of heat, precipitation and droughts has strengthened since the IPCC released its previous assessment in 2014.
As if the written projections were not dire enough, the nightly news provides plenty of grim visual support for the report’s findings. Raging fires in the west combined with the otherworldly scale of Hurricane Ida—which caused death and destruction as it charged through the south, the northeast and into large, metropolitan areas—drove home the message of the report all too clearly. With due respect to the climate deniers among us, the IPCC makes a highly compelling argument. As much as I had hoped for an alternative verdict, I’m more convinced than ever of our present crisis.
The State of Earth’s Climate
The report is organized in terms of four principal areas: 1) the current state of the climate, 2) climate futures, 3) climate facts in terms of risk assessment, and 4) limiting climate change. Each section consists of several of the IPCC’s scientific conclusions or projections, each with an assigned confidence level. A sampling of the conclusions made by the IPCC at various points in the report are reproduced below. These were supported with a high degree of confidence (90 to 100 percent). To avoid misstatements, these statements are reproduced verbatim from the IPCC’s Executive Summary:
1. It is unequivocal that human influence has warmed the atmosphere, ocean and land. Widespread and rapid changes in the atmosphere, ocean, cryosphere and biosphere have occurred.
2. Global surface temperature has increased faster since 1970 than in any other 50-year period over at least the last 2,000 years.
3. Global mean sea level has risen faster since 1900 than over any preceding century in at least the last 3,000 years.
4. Projected changes in extremes are larger in frequency and intensity with every additional increment of global warming.
5. The proportion of intense tropical cyclones (categories 4-5) and peak wind speeds of the most intense tropical cyclones are projected to increase at the global scale with increasing global warming.
These are just a few of the statements that give a reader pause. Aside from the observable trends that the IPCC describes, the report also discusses other complex dynamics and feedback loops at play, some of which the IPCC notes are presently irreversible. For example, the report points out that even if global CO2 emissions were to be reduced soon, the planet would continue to warm until at least mid-century as a result of existing and past emissions. Examples of irreversible trends include Arctic ice loss, sea-level rise and the thawing of permafrost, all of which are projected with high confidence to continue for decades and centuries to come.
Global- and Local-Scale Changes
The report concludes with several scenarios, each forecasting Earth’s climate given different levels of CO2 emissions. The two extremes on the spectrum, one in which CO2 emissions decline or reach net zero by 2050, and the other representing increasing CO2 emissions, project very different climate outcomes.
If global emissions continue unabated, the conditions we are experiencing now will be magnified in the form of more-extreme heat, winds, precipitation and weather events. The IPCC predicts with high confidence that under the extreme emissions scenario, global surface temperatures will exceed pre-industrial levels (1850-1910) by 4.4°C between 2081 and 2100.
If we dramatically reduce greenhouse gases by mid-century, the IPCC projects that global temperatures may gradually begin to dip below the 1.5°C point, to 1.4°C potentially, between 2081 and 2100. It should be noted that across all scenarios, due to past and current greenhouse gas emissions, the IPCC predicts it is more likely than not (and very likely under high-emission scenarios) that global temperatures will exceed pre-industrial levels by 1.5°C between 2021 and 2040.
Many countries have articulated carbon-neutral policies, but in nearly all cases these are still in the form of policy—not law. Some hope the UN’s upcoming climate conference in November 2021 will extract binding national commitments to reduce CO2 emissions from the world’s largest producers—notably China and the United States. We, as a global community, should be well beyond diplomatic hand wringing and empty, albeit well-meaning, debate at this point. The choices are stark, and the scientific basis for those choices has never been clearer. Frankly, my concern is whether world leadership can mobilize to even come close to what’s required. The word “sacrifice” is oddly relevant now. Can the world’s richest economies switch course and implement sweeping change? Can the United States?
As cities across the country frantically establish climate-resilience departments and stretch budgets for infrastructure redesigns and rebuilds, engineers act as the footsoldiers behind efforts to fortify and protect. The conditions under which we do our work have never been more in flux or less predictable. Records set for temperature, fire, rain, wind and a host of other parameters change—it would seem—by the day. Precipitation records set in New York state in late August were roundly broken in early September as Hurricane Ida swept through the region.
Engineers are problem solvers by profession, but, in many respects, we are pioneers as well—now more than ever. In the years ahead, lives and property are at stake as we experiment with new design and build standards as well as assess which mix of green infrastructure, materials and technologies make sense in a daunting new era of extremes.