History

As scorching heat grips large swaths of the Earth, a lot of people are trying to put the extreme temperatures into context and asking: When was it ever this hot before? Globally, 2023 has seen some of the hottest days in modern measurements, but what about farther back, before weather stations and satellites? Some news outlets have reported that daily temperatures hit a 100,000-year high. As a paleoclimate scientist who studies temperatures of the past, I see where this claim comes from, but I cringe at the inexact headlines. While this claim may well be correct, there are no detailed temperature records extending back 100,000 years, so we don’t know for sure. Here’s what we can confidently say about when Earth was last this hot. This is a new climate state Scientists concluded a few years ago that Earth had entered a new climate state not seen in more than 100,000 years. As fellow climate scientist Nick McKay and I recently discussed in a scientific journal art...

As a child growing up in the early 1990s, I remember learning in school about the greenhouse effect. Carbon dioxide released by burning fossil fuels traps heat near the Earth’s surface, like the glass of a greenhouse. I imagined myself on the playground, roasting inside a humid hothouse. Fast forward 30 years, and the terms have changed. For a while, “global warming” was the go-to expression for talking about rising global temperatures and the role of human activities, particularly the use of fossil fuels. It had a spike in internet searches in 2007, probably due to former Vice President Al Gore’s documentary “An Inconvenient Truth: A Global Warning,” which hit theaters in 2006. Near the end of the Obama administration, “climate change” became the most common term. It’s now trending in Google searches more than global warming. Both terms make the same point: Rising global temperatures have major consequences on local weather...

Over the past century, the Earth’s average temperature has swiftly increased by about 1 degree Celsius (1.8 degrees Fahrenheit). The evidence is hard to dispute. It comes from thermometers and other sensors around the world. But what about the thousands of years before the Industrial Revolution, before thermometers, and before humans warmed the climate by releasing heat-trapping carbon dioxide from fossil fuels? Back then, was Earth’s temperature warming or cooling? Even though scientists know more about the most recent 6,000 years than any other multimillennial interval, studies on this long-term global temperature trend have come to contrasting conclusions. To try to resolve the difference, we conducted a comprehensive, global-scale assessment of the existing evidence, including both natural archives, like tree rings and seafloor sediments, and climate models. Our results, published Feb. 15, 2023, suggest ways to improve climate forecasting to avoid missing some...

Some hurricanes are remembered for their wind damage or rainfall. Others for their coastal flooding. Hurricane Helene was a stew of all of that and more. Its near-record-breaking size, storm surge, winds and rainfall together turned Helene into an almost unimaginable disaster that stretched more than 500 miles inland from the Florida coast. At least 230 people died across Florida, Georgia, South Carolina, North Carolina, Tennessee and Virginia as Helene flooded towns, destroyed roads and bridges and swept away homes. In Florida, Helene’s storm surge caused damage along hundreds of miles of coast. As residents there cleaned up debris, another dangerous hurricane was headed their way. Some of the same areas hit hard by Helene on Sept. 26, 2024 – including Tampa Bay and Cedar Key – were forecast to see more flooding and an even higher storm surge in Tampa Bay from Hurricane Milton, expected to make landfall as early as Oct. 9. The majority of Helene’s vic...

At first glance, the connections between the world’s growing population and climate change seem obvious. The more people we have on this planet, the larger their collective impact on the climate. However, a closer look with a longer time horizon reveals relationships between population size and climate change that can help us better understand both humanity’s predicament as the global population hits 8 billion people – a milestone the United Nations marked on Nov. 15, 2022. Looking back to the Stone Age For much of human evolution, our ancestors were exposed to large climatic fluctuations between ice ages and intermittent warmer periods. The last of these ice ages ended about 10,000 years ago. Before the ice sheets melted, sea levels were about 400 feet (120 meters) lower than today. That allowed humans to migrate around the world. Everywhere they went, our ancestors reshaped landscapes, first by clearing forests and then through early agricultural practices...