As nations across the globe negotiate how to reduce their contributions to climate change, researchers at Penn are investigating just how the coming changes will impact the planet. What's clear is that the effect extends beyond simple warming. Indeed, the very physics and chemistry of the oceans are also shifting, and are forecast to change even more in the coming decades.

These changes have implications for, among other things, the single-celled organisms that comprise the base of the ocean's food web and are responsible for half of the world's photosynthetic activity: phytoplankton. Not only are phytoplankton sensitive to changes in climate, they also contribute to those changes, as they can remove carbon from the atmosphere and store it deep in the ocean when they die.

A micrograph of phytoplankton. Like plants on land, phytoplankton growth is controlled by environmental factors such as light, nutrients, and temperature.

Climate change is rapidly warming lakes around the world, threatening freshwater supplies and ecosystems, according to a new NASA and National Science Foundation-funded study of more than half of the world's freshwater supply.

Using more than 25 years of satellite temperature data and ground measurements of 235 lakes on six continents, this study -- the largest of its kind -- found lakes are warming an average of 0.61 degrees Fahrenheit (0.34 degrees Celsius) each decade. The scientists say this is greater than the warming rate of either the ocean or the atmosphere, and it can have profound effects.

The research, published in Geophysical Research Letters, was announced Wednesday at the American Geophysical Union meeting in San Francisco.

Do not underestimate the babbling brook. When it comes to greenhouse gases, these bucolic water bodies have the potential to create a lot of hot air. According to a new analysis in the journal Ecological Monographs, by researchers at the University of Wisconsin–Madison and colleagues, the world’s rivers and streams pump about 10 times more methane into our atmosphere than scientists estimated in previous studies.

As the Arctic warms, Greenland’s fringe of glaciers is thinning and melting—but the future of the Greenland ice sheet remains a giant question mark. Until recently, that was also true of the ice sheet’s past: Scientists have long debated whether it might have shrunk away to nothing during Earth’s warmest periods. Now, a new study suggests that Greenland was entirely ice free at some point in the last 1.25 million years.

“We should be worried about the Greenland Ice Sheet,” says Joerg Schaefer, a geochemist from Columbia University’s Lamont-Doherty Earth Observatory in Palisades, New York, and lead author of the findings, presented yesterday at the American Geophysical Union’s annual meeting here.

2015 has marked the International Year of Soils, an event that many members of the public missed — but they shouldn’t have, because soil is vitally important for human survival. Ominously, a study from the Grantham Centre for Sustainable Futures indicates that in the last 40 years, humans have chewed through 33 percent of the Earth’s topsoil, thanks to development and harmful farming practices. The grim findings are a bad sign for the future, as we rely on soil not just for sustenance, but also as a carbon trap, key component of nearly every ecosystem on Earth, and breeding ground for organisms with tremendous commercial and humanitarian applications, such as bacteria that could contribute to the development of cutting edge pharmaceuticals. We should be worshiping the ground we walk on, and this study indicates that we’ve been doing just the opposite.

Contrary to recent headlines — and a talk by actor Arnold Schwarzenegger at the United Nations Paris Climate Change Conference — eating a vegetarian diet could contribute to climate change. In fact, according to new research from Carnegie Mellon University, following the USDA recommendations to consume more fruits, vegetables, dairy and seafood is more harmful to the environment because those foods have relatively high resource uses and greenhouse gas (GHG) emissions per calorie. 

Climate negotiators meeting here in Paris have achieved a deal that could change the world. Conference chair and French foreign minister Laurent Fabius crowed that he had presided over a "historical turning point." Even when the hype has died down, that may turn out to be true. Even climate scientists who on Friday had sharply criticized an earlier draft of the text were convinced.  

The Paris Agreement commits the world to capping global warming to "well below 2 degrees Celsius above pre-industrial levels and pursuing efforts to limit the temperature increase to 1.5 degrees C." To achieve that, it requires the world to "reach global peaking of greenhouse gas emissions as soon as possible" and "to undertake rapid reductions thereafter, in accordance with best available science." 

Scientists are studying past changes in sea level in order to make accurate future predictions of this consequence of climate change, and they're looking down to Earth's core to do so. "In order to fully understand the sea-level change that has occurred in the past century, we need to understand the dynamics of the flow in Earth's core" says Mathieu Dumberry, a professor in physics at the University of Alberta.

The connection is through the change in the speed of Earth's rotation. Melt water from glaciers not only causes sea-level rise, but also shifts mass from the pole to the equator, which slows down the rotation. (Picture the Earth as a spinning figure skater. The skater moves his or her arms in to spin more quickly or out to slow down.) The gravity pull from the Moon also contributes to the slow down, acting a little like a leaver break. However, the combination of these effects is not enough to explain the observations of the slowing down of Earth's rotation: a contribution from Earth's core must be added.

The ongoing El Niño weather pattern in the Asia and Pacific is likely to be one of the strongest since 1998 and will continue into early 2016, according to a new United Nations advisory, which urges regional cooperation for early warning, in-season mitigation, and long-term adaptation strategies to curb climate risk.

“The impact of the 2015-2016 El Niño could be even more severe in certain locations, such as the uplands of Cambodia, central and southern India, eastern Indonesia, the central and southern Philippines, central and northeast Thailand...” stated the Third Advisory Note on El Niño issued jointly by the UN Economic and Social Commission for Asia and the Pacific (ESCAP) and the Regional Integrated Multi-Hazard Early Warning System for Africa and Asia (RIMES).

Lawrence Livermore researchers and collaborators have found that most climate models overestimate the increase in global precipitation due to climate change.

Specifically, the team looked at 25 models and found they underestimate the increase in absorption of sunlight by water vapor as the atmosphere becomes moister, and therefore overestimate increases in global precipitation.

The team found global precipitation increase per degree of global warming at the end of the 21st century may be about 40 percent smaller than what the models, on average, currently predict.