Global Warming

Global Warming Could Be Double What Models Predict

Another research study has suggested that global warming may be far worse than present predictive models suggest.

Researchers often use records of Earth’s past to predict changes in the future. A latest assessment of past warm periods shows that future global warming may be twice as warm as projected by climate models and sea levels may rise six meters or more with 2°C of warming.

A world that heats up by 2C is regarded as the limit for a climate-safe planet and 2015 Paris Climate Agreement aims to hold average global warming well below 2°C by reducing carbon emissions.

“Observations of past warming periods suggest that a number of amplifying mechanisms, which are poorly represented in climate models, increase long-term warming beyond climate model projections," said lead author Prof Hubertus Fischer from University of Bern. "This suggests the carbon budget to avoid 2°C of global warming may be far smaller than estimated, leaving very little margin for error to meet the Paris targets."

To make predictions, researchers looked at three past warm periods, the Holocene thermal maximum (5000-9000 years ago), the last interglacial (129,000-116,000 years ago) and the mid-Pliocene warm period (3.3-3 million years ago). During those periods, the temperatures were 0.5°C-2°C warmer than the pre-industrial temperatures of the 19th Century.

The warming of the first two periods was linked to predictable changes in the Earth's orbit, while the third period experienced increased levels of atmospheric carbon dioxide concentrations. The atmospheric carbon dioxide is also the main driver of the climate change today.

When researchers combined a wide range of measurements from ice cores, sediment layers, fossil records and other techniques, they were able to better predict future climate responses. Their result suggests that our today’s planet is warming much faster than any of these periods. Even if we curb carbon emissions, it would take centuries to millennia to reach equilibrium.

We can expect that sea-level rise could become unstoppable for millennia, impacting much of the world's population, infrastructure and economic activity.