Tag Archives: warming pause

Why a hot year matters more than a cold year or a neutral year

Earth’s systems are already out of balance. The comparative equilibrium we saw during most of the last 10,000 years meant that the amount of ice we had was roughly the amount of ice we were likely to get and keep at our current temperature and greenhouse gas level. When we increased the average temperature, that balance was shifted, and ice started melting in response to the increased temperature of the climate.

The “lull” between 1998 and 2015, which was not much of a lull, still saw accelerating ice melt, permafrost thawing, and sea level rise, because we had already raised the temperature enough to make those inevitable, based on our understanding of physics. Even a year that was down to the 1990 or 1980 temperature level, on average, followed by a return to 2000s temperatures, would have fairly little effect. The melting would have slowed, without stopping, and then sped up again when the temperature returned to the decadal “norm”.

But a dramatically hotter year – like this El Niño year – is a different matter. It injects a bunch more heat into the system, which means faster ice melt, and so lower albedo for the coming year, and more permafrost melt, and so more greenhouse gasses for the coming year, and more water evaporation, and so more greenhouse gasses for the coming year.

A single, unusually cold year, does not do much when we’re still above the temperature at which the current ice sheets formed, but a single hot year can create a spike of warming factors, which will cause even more warming in the years to come.

If we had not been emitting fossil fuels, it’s possible that the dip in global temperatures in the late 1960s/early 1970s would have led to more global cooling, and even an ice age – we’re certainly due for one – but we had already started the slowly accelerating process of global warming. We already had warming momentum, even back then, so we had a temporary cool period, and then when we came out of the 1970s, the temperature skyrocketed.

We’ll have more warming “pauses” in the future. That is a virtual certainty, but unless we re-balance the planet’s temperature budget by reducing greenhouse gases, the planet will just keep warming until it reaches a new equilibrium. Because of feedbacks like the albedo and the melting permafrost, even if we stop emitting CO2 now, the planet will keep warming for thousands of years, and the new equilibrium will be far, far hotter than anything our species has ever encountered.

There are a number of ways we could respond to this, but our best bet is to stop contributing to the problem, prepare for the changes we know are coming, and develop a strategy for deliberately managing the planet’s greenhouse gas levels.