How 2023 Broke Our Climate Models with Neil deGrasse Tyson & Gavin Schmidt

Climate Update: Why 2023 Was the Hottest Year on Record

Neil deGrasse Tyson and NASA Goddard climate scientist Gavin Schmidt (with co-host Paul) deliver a fast climate update focused on why 2023 became the hottest year on record and what that implies for climate models and future uncertainty.

Key points and arguments

• 2023 set a new temperature record by a large margin. Using global measurements—weather stations, ocean observations, and long-running temperature records—scientists reconstruct Earth’s temperature history back roughly 150 years. They emphasize that 2023 wasn’t just slightly the hottest year; it was a clear record jump on top of a long-term warming trend that has continued since the 1970s.

• Greenhouse-gas warming is well understood, but 2023 was still an uncomfortable surprise. The discussion notes that climate models and evidence strongly support that rising CO₂, methane, and other greenhouse gases drive warming. However, expectations for how much warming would occur in a particular year weren’t as high as what happened in 2023—especially because the year started with an El Niño/La Niña-related baseline, which typically affects year-to-year temperatures.

• Natural variability (El Niño/La Niña) couldn’t prevent the record. El Niño (warmer tropical Pacific) tends to produce warmer years, while La Niña tends to cool them. Historically, these patterns help forecast whether a year will be above or below the trend. But in 2023, the usual guidance didn’t translate into avoiding a record-hot year—raising concern about near-term prediction uncertainty.

• Solar cycle effects are included, but they’re relatively small. Schmidt addresses the ~11-year solar cycle. Changes in solar output can affect the stratosphere and produce relatively small temperature shifts—estimated around 0.05–0.1°C. Solar activity is accounted for, though predictions of the solar cycle still carry uncertainty.

• A major candidate for near-term surprises: aerosols (air particles). The panel highlights that aerosols (including PM2.5 from industry/agriculture) can cool the climate by reflecting sunlight. When countries reduce pollution, aerosol levels fall—removing part of that cooling and adding extra warming on top of greenhouse gases. They also stress that their ability to track everything precisely is limited and that better global aerosol measurements are needed.

• New satellite observations aim to reduce aerosol uncertainty. An upcoming satellite (scheduled for early February in the transcript) is intended to map atmospheric aerosol composition globally, improving constraints on particles and their effects in climate models.

• Aerosol “geoengineering” is discussed but viewed as non-viable. While reintroducing aerosols could cool the planet, Schmidt argues it poses major governance and stability problems: once started, it would be difficult to stop, potentially requiring operation for hundreds of years. Abrupt termination could trigger rapid “rebound” warming.

• If emissions stop increasing, warming would stop worsening. The discussion ends with a key reassurance: models indicate that if we stop increasing CO₂, global warming would level off rather than intensify further. The panel emphasizes that humans still have control over future outcomes, despite political and social disagreement.

• Ocean CO₂ uptake is real, but it isn’t “permanent cancellation.” Schmidt explains that about half of emitted CO₂ is taken up relatively quickly, but some of what’s absorbed can later re-enter the atmosphere. This means the system is only partly effective at removing CO₂ compared to what people might assume. Still, reducing emissions meaningfully lowers the ongoing buildup of atmospheric CO₂.

Overall conclusion / takeaway

• 2023 confirms strong, ongoing long-term greenhouse warming, but it also shows that year-to-year forecasting is less certain than hoped, likely due to factors like aerosols and natural variability interacting with greenhouse forcing.
• Improved observations, especially aerosol mapping, are expected to improve predictability.
• Action matters: stopping further emissions would prevent additional worsening, even though past emissions aren’t instantly erased.

Presenters or contributors

• Neil deGrasse Tyson
• Gavin Schmidt
• Paul (Paul “Mrio”/as introduced in the transcript)