Climate models underestimate sea ice melt and global warming

Climate models are essential tools for scientists, providing a glimpse into how our climate might change due to human-induced global warming.

As global temperatures continue to rise, these models help us predict and prepare for the impacts of an imminent climate crisis.

However, recent findings suggest that our trust in these models might be misplaced, as not all predictions are as accurate as we presume.

An ice-cold miscalculation

Right at the center of the stage, in a recently published investigation, stands the Energy Exascale Earth System Model (E3SM).

It is one of the common models employed by geoscientists, but recent research brings up substantial inaccuracies in its predictions.

This research was led by scientists in the Department of Earth System Science at UC Irvine and the University of Michigan Department of Climate and Space Sciences and Engineering.

The study revealed that the E3SM overestimates a critical component of our climate system – albedo, or the degree to which ice reflects sunlight back into space.

The researchers discovered that the E3SM incorrectly magnified the level of sunlight reflection from the ice, causing a miscalculation in predicting the planet’s warming.

“We found that with old model versions, the ice is too reflective by about five percent,” noted Chloe Clarke, the team’s project scientist.

Why does ice albedo matter?

The amount of sunlight received and reflected back by the Earth is paramount in determining the rate at which the planet will continue to heat up.

The E3SM’s overestimation of albedo stems from not considering what the team refers to as the “microphysical properties of ice.”

In simpler terms, these are factors such as algae and dust that can disrupt the ice’s reflecting capabilities. Dark-colored algae and dust can decrease reflectivity, making ice less effective at reflecting sunlight.

Dark ice absorbs more sunlight

“A large portion of melt from the Greenland Ice Sheet (GrIS) comes from regions with dark bare ice, because dark ice absorbs more incoming sunlight than regions with bright snow,” noted the study authors.

The experts pointed out that Earth System Models, which simulate changes in the Earth’s climate and the impacts of these changes, prescribe the reflectivity of these dark ice regions as a constant.

“This work shows that treating bare ice as though it has a constant reflectivity is not a good approximation, because the dark ice regions change as the winter snowpack melts and impurities accumulate on the ice surface.”

Estimates of sea ice melt

The team used satellite data to monitor the albedo of the Greenland Ice Sheet to demonstrate the inaccurate reflection rates in E3SM.

“The model estimates less melt than what would be expected from the ice microphysical properties,” stated Clarke.

The discovery of a more accurate ice reflectivity measurement predicted that the Greenland Ice Sheet is melting at a rate of about six gigatons more than older model versions estimated.

The ripple effect on climate modeling

These seemingly small inaccuracies can have considerable implications. The team hopes their findings will bolster the efficiency of climate models, illuminating the significance of snow and ice-related climate feedbacks.

The experts now plan to extend their research beyond Greenland. The goal is to get it functional globally and not just valid over Greenland, explained Clarke. This will include applying the findings to glaciers in other regions, such as the Andes and Alaska, to measure the accuracy of the new ice albedo.

Our understanding of the Earth’s climate is intricate and ever-evolving. This important work allows us to inch closer to a more accurate prediction of our planet’s future, unraveling the complexities of our changing climate one small step at a time.

Enhancing the accuracy of climate models

As the science of climate modeling continues to advance, the focus on accuracy is more crucial than ever.

Enhancements in climate models, such as the improved understanding of ice albedo, provide more reliable data for predicting future climate scenarios.

These enhancements allow policymakers and scientists to make more informed decisions about climate action.

With continued research and collaboration, we can refine these models to reflect the complexities of the Earth’s climate system more precisely, ensuring that our strategies to combat climate change are based on the best available science.

The study is published in the Journal of Geophysical Research: Atmospheres.

Image Credit: NASA/Goddard Space Flight Center Conceptual Image Lab

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