Natural gas, long seen as a cleaner replacement to coal and an important tool in the fight to slow global warming, can be just as harmful to the climate, a new study has concluded, unless companies can cut the leaks (泄露), since it takes as little as 0.2 percent of gas to leak to make natural gas as big a driver of climate change as coal.

The study, which involved researchers from Harvard and Duke Universities and NASA, pokes holes in the idea that natural gas is suitable energy resources to a future powered entirely by renewables, like solar and wind. “Even if gas leaks little, it’s as bad as coal,” said Deborah, the lead researcher. “It can’t be considered a good bridge, or replacement.”

When power companies generate electricity by burning natural gas instead of coal, they produce only half the amount of planet-warming CO₂. But natural gas is made up mostly of me thane (甲烷), which is, in the short term, a far more powerful planet-warming gas than CO₂, when it escapes unburned into the atmosphere. And there’s increasing evidence that methane is leaking from gas systems in far larger quantities than previously thought.

There are other balances to consider. The CO₂ produced by coal-burning power plants lasts far longer in the atmosphere than methane, whose climate effects disappear after a few decades. So focusing on methane leaks from gas systems as a way to control carbon emissions (碳排放) means the world might reduce some short-term warming, but still face a dangerous rise in average temperatures many decades into the future. That said, with the consequences of climate change already spreading around the world, controlling methane would be a way that works faster to slow warming.

“I do hope the world pays attention to this, as I fear too many remain too concentrated on simply reducing coal use, even if it results in more gas consumption,” Deborah said. “What the world requires is to move to a 100 percent renewable energy future as soon as possible.”

For years, scientists have debated whether humans or the climate have caused the population of large mammals to decline dramatically over the past several thousand years. A new study from Aarhus University confirms that climate cannot be the explanation.

About 100,000 years ago, the first modern humans migrated out of Africa in large numbers. They were very good at adapting to new habitats, and they settled in almost every kind of landscape — from deserts to jungles to the icy taiga in the far north.

Part of the success was human’s ability to hunt large animals. With clever hunting techniques and specially built weapons, they perfected the art of killing even the most dangerous mammals.

But unfortunately, the great success of our ancestors came at the expense of the other large mammals.

It is well-known that numerous large species went extinct during the time of worldwide colonization by modern humans. Now, new research from Aarhus University reveals that those large mammals that survived also experienced a dramatic decline.

By studying the DNA of 139 living species of large mammals, scientists have been able to show that the abundances of almost all species fell dramatically about 50,000 years ago. This is according to Jens-Christian Svenning, a professor and head of the Danish National Research Foundation’s Center for Ecological Dynamics in a Novel Biosphere (ECONOVO) at Aarhus University and the initiator of the study.

“We’ve studied the evolution of large mammalian populations over the past 750,000 years. For the first 700,000 years, the populations were fairly stable. But 50,000 years ago, the populations fell dramatically and never recovered,” he says, and continues: “For the past 800,000 years, the globe has fluctuated (波动) between ice ages and interglacial periods about every 100,000 years. If the climate was the cause, we should see greater fluctuations when the climate changed 50,000 years earlier.But we don’t. Humans are, therefore, the most likely explanation.”

Each year, the world loses about 10 million hectares of forest — an area about the size of Iceland — because of cutting down trees. At that rate, some scientists predict the world’s forests could disappear in 100 to 200 years. To handle it, now researchers at Massachusetts Institute of Technology (MIT) have pioneered a technique to generate wood-like plant materials in a lab. This makes it possible to “grow” a wooden product without cutting down trees.

In the lab, the researchers first take cells from the leaves of a young plant. These cells are cultured in liquid medium for two days, then moved to another medium which contains nutrients and two different hormones (激素). By adjusting the hormone levels, the researchers can tune the physical and mechanical qualities of the cells. Next, the researchers use a 3D printer to shape the cell-based material, and let the shaped material grow in the dark for three months. Finally, the researchers dehydrate (使脱水) the material, and then evaluate its qualities.

They found that lower hormone levels lead to plant materials with more rounded, open cells of lower density (密度), while higher hormone levels contribute to the growth of plant materials with smaller but denser cell structures. Lower or higher density of cell structures makes the plant materials softer or more rigid, helping the materials grow with different wood-like characteristics. What’s more, it’s to be noted that the research process is about 100 times faster than the time it takes for a tree to grow to maturity!

Research of this kind is ground-breaking. “This work demonstrates the great power of a technology,” says lead researcher, Jeffrey Berenstain. “The real opportunity here is to be at its best with what you use and how you use it. This technology can be tuned to meet the requirements you give about shapes, sizes, rigidity, and forms. It enables us to ‘grow’any wooden product in a way that traditional agricultural methods can’t achieve.”