Fact check: +2.7°C is only the new "conservative" estimate. James Hansen is predicting 4.5 to 4.8°C by 2100.

1. Summary of the results

The statement accurately reflects James Hansen's current predictions, though the full context is more complex. Hansen indeed predicts warming of 4.5-4.8°C by 2100 ^{[1] [2]}, which is significantly higher than previous IPCC estimates of 3°C ^[1]. His longer-term predictions suggest temperatures could rise between 8°C and 10°C above pre-industrial levels over several hundred years ^[3]. The immediacy of the situation is highlighted by the fact that 2024 was the first year global temperatures exceeded 1.5°C above pre-industrial levels ^[4].

2. Missing context/alternative viewpoints

Several important contextual elements are missing from the original statement:

• Hansen's track record is contested, with some sources noting that many of his previous climate models and forecasts have not accurately predicted temperature changes ^[5]
• There are significant uncertainties in climate modeling, even while acknowledging the possibility of Hansen's predictions being accurate ^[6]
• Hansen believes the 2°C target is now "impossible" and expects temperatures to reach 2°C by 2045 ^{[7] [8]}
• The climate appears to be more sensitive to CO2 than previously thought ^[2]

3. Potential misinformation/bias in the original statement

While the statement itself isn't misleading, it presents Hansen's predictions without important caveats:

• It doesn't mention that there's scientific debate about the accuracy of these predictions
• The statement could benefit various stakeholders:
• Climate action advocates could use these higher estimates to push for more urgent policy changes
• Climate skeptics could point to Hansen's previous prediction track record to dismiss these estimates ^[5]
• Research institutions might benefit from increased funding for climate research due to heightened concerns
• The presentation of 2.7°C as "conservative" needs to be contextualized against the IPCC's previous estimates of 2.5°C to 4°C ^[2], as it sits within this range rather than being notably conservative