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Climate models are complex and mirror the chaotic flow of Earth’s atmosphere and oceans. Despite their complexity, critics often argue that these models are too uncertain to help understand present-day warming or predict future changes. However, early climate models made specific forecasts about global warming decades before observations could confirm them, and when they did, the models were right.
The earliest climate models predicted both the magnitude and geographical patterns of warming. These predictions started in the 1960s at a government laboratory outside Princeton, New Jersey: the Geophysical Fluid Dynamics Laboratory (GFDL). Many of these early predictions stemmed from the work of Syukuro Manabe, who was awarded the Nobel Prize in Physics in 2021 for his contributions.
Manabe’s models forecasted global warming based on atmospheric and ocean physics. Here are five key forecasts that were right:
**Forecast No. 1: Global Warming from CO2**
In the 1960s, Manabe modeled the greenhouse effect to show how carbon dioxide traps heat in Earth’s atmosphere. His simple model predicted a temperature increase of about 5.4°F (3°C) with doubled atmospheric CO2 levels, which remains accurate today.
**Forecast No. 2: Stratospheric Cooling**
Manabe’s models showed that as CO2 concentrations increased, the surface and lower atmosphere warmed while the stratosphere cooled. This cooling is a distinctive fingerprint of carbon dioxide-driven warming, confirmed by decades of satellite measurements.
**Forecast No. 3: Arctic Amplification**
In 1975, Manabe simulated global warming with his quasi-global model and found that the Arctic warms significantly more than other regions, by about two to three times as much. This Arctic amplification is a robust feature of global warming, evident in both present-day observations and subsequent simulations.
**Forecast No. 4: Land-Ocean Contrast**
Manabe’s coupled atmospheric-ocean models around 1990 predicted that land generally warms more than the ocean by about 50%, which is consistent with observed warming patterns.
**Forecast No. 5: Delayed Southern Ocean Warming**
The Southern Ocean encircling Antarctica was found to warm very slowly due to its continual upwelling of cold deep waters, a phenomenon visible in temperature observations.
Looking back on Manabe’s work today, it’s clear that even early climate models captured the broad strokes of global warming decades before they were observed. While models have limitations, particularly regarding regional predictions, the success of these early forecasts provides confidence in interpreting current changes and predicting future ones.
