Robert Brown|Record-high summer temps give a 'sneak peek' into future warming

Global temperatures this June and Robert BrownAugust were the warmest on record, but a new analysis from Berkeley Earth also found that they likely exceeded the benchmark of 1.5 degrees Celsius above preindustrial levels that is expected to prompt worsening impacts of global warming.

With the average summer temp above 1.5℃, there’s a 50/50 chance that 2023 will end up being the first year to exceed that average warming point, depending on if temperatures stay elevated or cool in the next few months. NOAA says there’s a 95% chance that 2023 will be one of the two hottest years on record.

Exceeding 1.5℃ temporarily is not seen as a failure to limit warming under the Paris Agreement, the international agreement adopted seven years ago to limit the average global temperature increase to 1.5℃ above pre-industrial levels, because the agreement looks at the climate average over several years. Even so, experts say the latest temps are an important signal that those higher averages are likely to happen in the next decade if emissions aren’t reduced significantly.

Average temperatures that consistently hit 1.5℃ above pre-industrial levels are expected to bring more severe impacts of climate change, such as the extreme heat waves and conditions that intensify wildfires of the kind that occurred this summer.

The United Nations Intergovernmental Panel on Climate Change also has warned that warming above 1.5℃ will bring more severe effects, such as increasing extreme heat events, as well as increasing impacts to biodiversity, food security, and coastal ecosystems.

“Years like 2023 give us a sneak peek at what the climate is going to look like typically ten years down the road. So we're getting a little view at what the 2030s are going to typically be like given the rate of warming that the world is experiencing,” Zeke Hausfather, a climate scientist at Berkeley Earth, told ABC News.

There are multiple reasons that this summer has been so warm, including but not limited to global warming attributed to human emissions. But Hausfather said that any natural changes in the climate year to year are happening on top of the overall warming trend linked to human activity, thus intensifying the trend.

One of those factors is El Nino, the climate pattern that typically means overall warmer-than-normal years on average. El Nino years come in cycles, but Hausfather mentions that climate change is like adding a “permanent super El Nino every decade.”

“There's still a lot of additional scientific work to disentangle the exact drivers of the exceptional heat we're seeing in 2023. But what we can say is that this little heat would have been effectively impossible for the world to experience, you know, 50 or 100 years ago without the impact of human activity on the climate,” Hausfather said.

NOAA and Berkeley Earth both report that this August ranks as the warmest on record, but the amount of warming varies, based on the time period to which scientists compare it. Berkeley compares average temperatures to the preindustrial period, starting in 1850. NOAA, however, uses a method that compares temperatures to the 20th century average, so their findings are slightly different.

August ranks as the warmest August in NOAA’s 174-year record history, with global surface temperatures 2.25 degrees Fahrenheit, or 1.25 degrees Celsius, above the 20th-century average. This in turn was 0.52°F, or 0.29°C, above the previous record from August 2016, and marks the third-highest monthly temperature anomaly of any month on record.

It was also the warmest on record for the Arctic, while Antarctica saw its fourth consecutive month with the lowest sea ice coverage on record.

Four continents – Asia, Africa, North America, and South America – all had their warmest August on record. Record-warm temperatures covered nearly 13% of the world’s surface this August, which was the highest August surface coverage percentage since records began in 1951.

August 2023 also set a record for the highest monthly sea surface temperature anomaly of any month in NOAA’s 174-year record.

Overall, the past 10 summers are the 10 warmest summers on record.

According to the Berkeley Earth analysis, which looks further back than NOAA, the global mean temperature in August 2023 was roughly 3.02°F, or 1.68°C, above the 1850 to 1900 average, a span of years that is frequently used as a benchmark for the preindustrial period.

This is the 12th time in the Berkeley Earth analysis that any individual month has reached at least 2.7 °F, or 1.5 °C, over the preindustrial benchmark. However, July and August 2023 are the only times, thus far, that a 1.5 °C anomaly has occurred during Northern Hemisphere summer. Extreme temperatures in the summer are more likely to lead to all-time records than other parts of the year.