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These Are the Biggest Climate Questions for the New Decade
The 2010s brought major climate science advances, but researchers still want to pin down estimates of Arctic melt and sea level rise, Scientific Amrican , By Chelsea Harvey, E&E News on January 4, 2020 The 2010s were almost certainly the hottest decade on record — and it showed. The world burned, melted and flooded. Heat waves smashed temperature records around the globe. Glaciers lost ice at accelerating rates. Sea levels continued to swell.

At the same time, scientists have diligently worked to untangle the chaos of a rapidly warming planet.

In the past decade, scientists substantially improved their ability to draw connections between climate change and extreme weather events. They made breakthroughs in their understanding of ice sheets. They raised critical questions about the implications of Arctic warming. They honed their predictions about future climate change.

The 2010s were almost certainly the hottest decade on record — and it showed. The world burned, melted and flooded. Heat waves smashed temperature records around the globe. Glaciers lost ice at accelerating rates. Sea levels continued to swell.

At the same time, scientists have diligently worked to untangle the chaos of a rapidly warming planet.

In the past decade, scientists substantially improved their ability to draw connections between climate change and extreme weather events. They made breakthroughs in their understanding of ice sheets. They raised critical questions about the implications of Arctic warming. They honed their predictions about future climate change.

Some of these links are straightforward. Melting Arctic ice pouring into the ocean can raise global sea levels. Thawing permafrost can release large amounts of carbon dioxide and methane into the atmosphere, potentially accelerating the rate of global warming.

Others are more contentious.

In the last decade, a growing scientific debate has arisen about the influence of Arctic warming on global climate and weather patterns, particularly in the midlatitudes……..

One ongoing project known as the Polar Amplification Model Intercomparison Project is conducting a series of coordinated model experiments, all using the same standard methods, to investigate the Arctic climate and its connections to the rest of the globe. Experts say these kinds of projects may help explain why modeling studies conducted by different groups with different methods don’t always get the same results.

Outside that debate, there are still big questions about the Arctic climate to resolve. Scientists know the Arctic is heating up at breakneck speed — but they’re still investigating all the reasons why.

Researchers believe a combination of feedback processes are probably at play. Sea ice and snow help reflect sunlight away from the Earth. As they melt away, they allow more heat to reach the surface, warming the local climate and causing even more melting to occur…….

OCEANS AND ICE

Sea-level rise is one of the most serious consequences of climate change, with the potential to displace millions of people in coastal areas around the world.

At the moment, the world’s oceans are rising at an average rate of about 3 millimeters each year. It appears to be speeding up over time. That may not sound like much, but scientists are already documenting an increase in coastal flooding in many places around the world……..

Some scientists worry that as ice loss continues to speed up in both Greenland and Antarctica, parts of the ice sheets could eventually destabilize and collapse entirely — leading to catastrophic sea-level rise.

In recent years, scientists have discovered that warm ocean currents are helping to melt some glaciers from the bottom up, both in Greenland and particularly in parts of West Antarctica. Better understanding the relationship between oceans and ice is a key priority for glacier experts, Tedesco said.

At the same time, monitoring the way water melts and moves along the top of the ice is also a major priority. In Greenland, climate-driven changes in the behavior of large air currents like the jet stream may be helping to drive more surface melting…….

EXTREME WEATHER EVENTS

The past decade saw leaps and bounds in a field of climate research known as “attribution science” — the connection between climate change and extreme weather events.

It was once thought to be impossible, but scientists are now able to estimate the influence of global warming on individual events, like heat waves or hurricanes. In the past few years alone, scientists have found that some events are now occurring that would have been impossible in a world with no human-caused climate change.

As attribution science has advanced, researchers have been able to tackle increasingly complex events, like hurricanes and wildfires, which were previously too complicated to evaluate with any confidence. They’ve gotten faster, too — researchers are now able to assess some extreme events nearly in real time.

Some organizations are working to develop sophisticated attribution services, similar to weather services, which would release analyses of extreme events as soon as they occur. The German national weather service; the United Kingdom’s Met Office; and the Copernicus program, part of the European Centre for Medium-Range Weather Forecasts, have all begun exploring these kinds of projects.

At the same time, scientists are working to improve their predictions of future extreme events in a warming world.

So far, climate models predict that many extreme weather events will happen more frequently, or will become more severe, as the climate continues to change. Heat waves will be hotter, hurricanes will intensify, heavy rainfall events may happen more frequently in some places, and droughts may be longer in others…….

PROJECTING THE FUTURE

Predicting how much the Earth will warm, given a certain level of greenhouse gas emissions, may seem like the simplest goal of climate modeling. But it’s harder than it sounds.

Climate models don’t always agree on the Earth’s exact sensitivity to greenhouse gas emissions — although they do tend to fall within a certain range. If global carbon dioxide concentrations were to double, for instance, models from the past decade have tended to predict that the Earth would warm from between 1.5 and 4.5 degrees Celsius……. https://www.scientificamerican.com/article/these-are-the-biggest-climate-questions-for-the-new-decade/?amp