2023 Likely to be Among the Coolest in 20 Years

Not the coolest in the last 20 years, but the coolest in the next 20.

News about temperature extremes keeps getting, well, more extreme! The September 2023 global temperature data is simply extraordinary. The average global temperature for last month set the record for September by a half-degree Celsius (nearly a whole degree Fahrenheit)! That’s hard to fathom.

Color-coding in this graph shows very clearly the warming trend that has existed in recent decades—as well as the record anomalies in June through September, 2023. Source: Berkeley Earth

In a guest opinion piece in the New York Times on October 13^th, Dr. Zeke Hausfather, a climate scientist with Berkeley Earth (and with whom I had been on a resilience team advising a Bay Area tech company two years ago), said that he and his climate scientist colleagues “have just about run out of adjectives to describe what we have seen.”

And the record temperature in September follows a new record in August and in July and in June… The charts are pretty dramatic, and there is now a near certainty that 2023 will set an all-time record for global temperature, according to Dr. Robert Rohde, of Berkeley Earth.

NOAA also predicts that 2023 will be the warmest on record globally. Hausfather’s piece in the Times suggests that the warming curve has grown steeper since the 1970s—i.e., the rate of warming is accelerating. Berkeley Earth now predicts that there is a 90% chance that the global average temperatures for 2023 will exceed 1.5°C above the 1850-1900 reference period—for the first time ever. (1.5°C, or 2.7°F, is one of those not-to-exceed benchmarks identified by IPCC.)

A graph showing average global September temperatures going back to 1850. September 2023 was 1.82°C above the 1850-1900 average. This set a new record for the greatest monthly temperature anomaly. Source: Berkeley Earth

But here’s the thing: despite all this shocking data about record global temperatures, if the current trend continues, 2023 could turn out to be one of the coolest in my four-year-old grandson’s life. Think about that for a minute….

Down-the-road a few decades, we may well look back on the 2020s as the Pleasant ’20s. If the more troubling climate models prove accurate, we could well be enjoying the waning years of a temperate climate throughout significant regions of the U.S.—and the world.

A visualization showing September temperatures in 2023 compared with September temperatures during the period 1951 to 1980. The image also shows strengthening El Niño conditions in the equatorial Pacific—which will exacerbate warming air temperatures. Source: Berkeley Earth

Despite what a lot of people say, this isn’t the “new normal.” Normal would imply a plateau in conditions, and that’s not likely to happen any time soon. Until we actually eliminate our net greenhouse gas emissions (carbon dioxide, methane, and other greenhouse gases) or come up with ways to intervene in global climate change, we can expect a long-term upward trend.

What this means for thermal modeling and sizing HVAC equipment

The way we currently model energy performance in buildings, and size heating, ventilation, and air-conditioning (HVAC) equipment, is to look up the weather data for a reasonably close location using the typical meteorological year (TMY). TMY data for the U.S. is compiled and reported by the National Renewable Energy Laboratory (NREL) through the National Solar Radiation Database.

TMY datasets include data on average solar radiation, wind speed, and air temperature, and they are available in various formats from NREL for hundreds of locations in the U.S., and these are used in modeling building performance. Periodically, the datasets are updated.

The first TMY dataset covered the period between 1948 and 1980 and included meteorological data for 229 locations in the U.S. The second dataset, TMY2, provided average conditions for 239 locations in the U.S., averaging conditions from 1961 to 1990, and with this dataset, a precipitation column was added.

The current dataset, TMY3, includes 1,020 locations throughout the U.S., Guam, Puerto Rico, and the U.S. Virgin Islands. For most of these locations, TMY3 covers the period 1976–2005; for all other locations it is based on collected data from 1991–2005.

The creators of EnergyPlus energy modeling software at NREL have recently introduced the TMYx data set that is based on 2006-2021 conditions for 16,000 locations worldwide, though that dataset is not yet as easily available.

The problem with TMY datasets, even the latest, is that the meteorological data on which they are based is old. When the climate was relatively stable, that was fine, but it’s no longer stable, as can be seen in graphs like those shown above.

Ariane Laxo, the Director of Sustainability at HGA, created the graphic below to convey just how problematic it is to use TMY data for energy modeling. The red, dashed, horizontal line near the bottom shows the predicted number of extreme-heat days (over 103.9°F) per year in Sacramento, California, based on TMY data. If this is used to model the performance of a building being designed today that will go into use in 2025, the predicted extreme heat days per year during its expected lifespan (assuming a moderate-carbon-emission scenario: RCP 4.5) are shown in the grayed area to the right on the timeline axis. The likely days with extreme heat will wildly exceed the predictions based on TMY data.

Graph comparing actual and predicted extreme heat days and—in the dashed red line near the bottom—the number of extreme heat days in a Typical Meteorological Year. Source: Ariane Laxo, HGA

Moving forward

Fortunately, a lot of smart people and organizations recognize the limitations of the current TMY data and the need for tools for modeling future conditions. The international engineering firm Arup launched WeatherShift several years ago—a tool for accessing future weather data for use in energy modeling.

Cal-Adapt is an initiative of the State of California to make California climate data available for use in modeling future conditions in all locations of the State. Cal-Adapt offers data related to not only temperature projections, but also precipitation, sea level rise, drought, wildfire, and other climate-related information.

The bottom-line, relative to building design, is that it’s a whole new world out there. In designing our buildings and modeling their performance, we should be looking ahead, rather than looking back. The world is getting warmer—a lot warmer—and our designs should be taking that into account.

It’s not only temperatures that concern us. While the cause of dramatically reduced sea ice in the Antarctic in 2023 hasn’t been determined, the deviation from data going back to 1979 (shown here) is striking. 2023 data is shown by the line falling well below the others. Source: Berkeley Earth

Along with designing buildings to function well in significantly warmer conditions, we should be designing them to do all right during significant disruptions, including loss of power. That’s where the concept of passive survivability comes into play.

Note: The graphs presented here can be found, along with others, in Berkeley Earth’s September 2023 Temperature Update, which is an excellent source of climate information.

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Along with founding the Resilient Design Institute in 2012, Alex is founder of BuildingGreen, Inc. To keep up with his latest articles and musings, you can sign up for his Twitter feed. To receive e-mail notices of new blogs, sign up at the top of the page.

David W. Orr, Ph.D

David W. Orr is Paul Sears Distinguished Professor of Environmental Studies & Politics, Emeritus. He also served as “Counselor to the President” of Oberlin College for ten years. He is the author of eight books, including Dangerous Years: Climate Change and the Long Emergency (Yale, 2016) and Down to the Wire: Confronting Climate Collapse (Oxford, 2009) and co-editor of three others. He has authored over 220 articles, reviews, book chapters, and professional publications. In the past twenty-five years he has served as a board member or adviser to ten foundations and on the Boards of many organizations including the Rocky Mountain Institute, Bioneers, and the Aldo Leopold Foundation.

He is currently a Trustee of the Alliance for Sustainable Colorado, Children and Nature Network, and the WorldWatch Institute. He has been awarded nine honorary degrees and a dozen other awards including a Lyndhurst Prize, a National Achievement Award from the National Wildlife Federation, leadership awards from the U.S. Green Building Council (2014) and from Second Nature (2012), and a lifetime achievement award from Green Energy Ohio and the North American Association for Environmental Education. He has lectured at hundreds of colleges and universities throughout the U.S., Europe, Latin America, and Asia. He headed the effort to design, fund, and build the Adam Joseph Lewis Center, which was named by an AIA panel in 2010 as “the most important green building of the past thirty years,” as “one of thirty milestone buildings of the twentieth century” by the U.S. Department of Energy, and as one of “52 game-changing buildings of the past 170 years” by the editors of Building Design +Construction in January, 2016. He was instrumental in the design and funding of the Peter B. Lewis Gateway Center. He is the founder of the Oberlin Project and a founder of the journal Solutions. His current work is on the state of American democracy.