Day: June 4, 2019

Read the full story in Newsweek.

Carbon dioxide concentrations in Earth’s atmosphere have reached 415 parts per million—a level that last occurred more than three million years ago, long before the evolution of humans. This news adds to growing concern that climate change will likely wreak serious damage on our planet in the coming decades.

While Earth has not been this warm in human history, we can learn about coping with climate change by looking to the Classic Maya civilization that thrived between A.D. 250-950 in Eastern Mesoamerica, the region that is now Guatemala, Belize, Eastern Mexico, and parts of El Salvador and Honduras.

Many people believe that the ancient Maya civilization ended when it mysteriously “collapsed.” And it is true that the Maya faced many climate change challenges, including extreme droughts that ultimately contributed to the breakdown of their large Classic Period city-states.

However, the Maya did not disappear: Over 6 million Maya people live mainly in Eastern Mesoamerica today. What’s more, based on my own research in the Northern Yucatan Peninsula and work by my colleagues throughout the broader Maya region, I believe Maya communities’ ability to adapt their resource conservation practices played a crucial role in allowing them to survive for as long as they did. Instead of focusing on the final stages of Classic Maya civilization, society can learn from the practices that enabled it to survive for nearly 700 years as we consider the effects of climate change today.

Read the full story at The Conversation.

Antarctica is further from civilisation than any other place on Earth. The Greenland ice sheet is closer to home but around one tenth the size of its southern sibling. Together, these two ice masses hold enough frozen water to raise global mean sea level by 65 metres if they were to suddenly melt. But how likely is this to happen?

The Antarctic ice sheet is around one and half times larger than Australia. What’s happening in one part of Antarctica may not be the same as what’s happening in another – just like the east and west coasts of the US can experience very different responses to, for example, a change in the El Niño weather pattern. These are periodic climate events that result in wetter conditions across the southern US, warmer conditions in the north and drier weather on the north-eastern seaboard.

The ice in Antarctica is nearly 5km thick in places and we have very little idea what the conditions are like at the base, even though those conditions play a key role in determining the speed with which the ice can respond to climate change, including how fast it can flow toward and into the ocean. A warm, wet base lubricates the bedrock of land beneath the ice and allows it to slide over it.

These issues have made it particularly difficult to produce model simulations of how ice sheets will respond to climate change in future. Models have to capture all the processes and uncertainties that we know about and those that we don’t – the “known unknowns” and the “unknown unknowns” as Donald Rumsfeld once put it. As a result, several recent studies suggest that previous Intergovernmental Panel on Climate Change reports may have underestimated how much melting ice sheets will contribute to sea level in future.