Scientific research

About 400,000 years ago, large parts of Greenland were ice-free. Scrubby tundra basked in the Sun’s rays on the island’s northwest highlands. Evidence suggests that a forest of spruce trees, buzzing with insects, covered the southern part of Greenland. Global sea level was much higher then, between 20 and 40 feet above today’s levels. Around the world, land that today is home to hundreds of millions of people was under water. Scientists have known for awhile that the Greenland ice sheet had mostly disappeared at some point in the past million years, but not precisely when. In a new study in the journal Science, we determined the date, using frozen soil extracted during the Cold War from beneath a nearly mile-thick section of the Greenland ice sheet. A brief look at the evidence beneath Greenland’s ice sheet and the lessons its holds. The timing – about 416,000 years ago, with largely ice-free conditions last...

When a hurricane hits land, the destruction can be visible for years or even decades. Less obvious, but also powerful, is the effect hurricanes have on the oceans. In a recent study, we show through real-time measurements that hurricanes don’t just churn water at the surface. They can also push heat deep into the ocean in ways that can lock it up for years and ultimately affect regions far from the storm. Heat is the key component of this story. It has long been known that hurricanes gain their energy from warm sea surface temperatures. This heat helps moist air near the ocean surface rise like a hot air balloon and form clouds taller than Mount Everest. This is why hurricanes generally form in tropical regions. What we discovered is that hurricanes ultimately help warm the ocean, too, by enhancing its ability to absorb and store heat. And that can have far-reaching consequences. How hurricanes draw energy from the ocean’s...

Some of the world’s most popular museums are natural history collections: Think of dinosaur fossils, gemstones and preserved animals. Herbaria – collections of pressed, dried plant specimens – are a less-known but important type of natural history collection. There are some 400 million botanical specimens stored across over 3,500 herbaria around the world, but most are not widely publicized and rarely host public exhibits. I study biodiversity and global change, and these collections have fueled my work. My collaborators and I have used herbarium collections to study how flowering times respond to changes in climate, how dispersal traits and environmental preferences affect the likelihood that plants will become invasive, and how fires affect tropical biodiversity. I have had easy access to specimens from every corner of the world, but most researchers are not as lucky. This is partly because herbaria as we know them today are largely a European creation. And...

Henry David Thoreau, the environmental philosopher and author of “Walden”, was a keen observer of seasonal change. In 1862, for example, he wrote in the Atlantic Monthly: “October is the month of painted leaves. Their rich glow now flashes round the world. As fruits and leaves and the day itself acquire a bright tint just before they fall, so the year near its setting. October is its sunset sky; November the later twilight.” Over the past 20 years, researchers have used Thoreau’s observations of plant flowering, leaf emergence on trees and shrubs, bird migration and spring ice melt on Walden Pond to study how these events have changed since the 1850s, largely in response to climate change. Ecologists have also pulled data for modern-day research from museum specimens, journals of hunting guides and bird and butterfly club reports. Comparisons with historical records have provided insights into shifts in the natural world caused by climate chang...