what is a global warming

 Since the Industrial Revolution, the global annual temperature has increased in total by a little more than 1 degree Celsius, or about 2 degrees Fahrenheit. Between 1880 the year that accurate record keeping began and 1980, it rose on average by 0.07 degrees Celsius (0.13 degrees Fahrenheit) every 10 years. Since 1981, however, the rate of increase has more than doubled: For the last 40 years, we’ve seen the global annual temperature rise by 0.18 degrees Celsius, or 0.32 degrees Fahrenheit, per decade. The result, A planet that has never been hotter. Nine of the 10 warmest years since 1880 have occurred since 2005 and the 5 warmest years on record have all occurred since 2015. Climate change deniers have argued that there has been a “pause” or a “slowdown” in rising global temperatures, but numerous studies, including a 2018 paper published in the journal Environmental Research Letters, have disproved this claim. The impacts of global warming are already harming people around the world. Now climate scientists have concluded that we must limit global warming to 1.5 degrees Celsius by 2040 if we are to avoid a future in which everyday life around the world is marked by its worst, most devastating effects: the extreme droughts, wildfires, floods, tropical storms, and other disasters that we refer to collectively as climate change. These effects are felt by all people in one way or another, but are experienced most acutely by the underprivileged, the economically marginalized, and people of color, for whom climate change is often a key driver of poverty, displacement, hunger, and social unrest. More than half the global ocean experiences high temperatures that were rare a century ago, Yesterday’s scorching ocean extremes are today’s new normal. A new analysis of surface ocean temperatures over the past 150 years reveals that in 2019, 57 percent of the ocean’s surface experienced temperatures rarely seen a century ago, researchers report February 1 in PL OS Climate. To provide context for the frequency and duration of modern extreme heat events, marine ecologist's nisei Tanaka, now at the National Oceanographic and Atmospheric Administration in Honolulu, and Kyle Van Houston, now at the Loggerhead Marine life Center in Juno Beach, Fla., analyzed monthly sea-surface temperatures from 1870 through 2019, mapping where and when extreme heat events occurred decade to decade. Looking at monthly extremes rather than annual averages revealed new benchmarks in how the ocean is changing. More and more patches of water hit extreme temperatures over time, the team found. Then, in 2014, the entire ocean hit the “point of no return,” Van Houston says. Beginning that year, at least half of the ocean’s surface waters saw temperatures hotter than the most extreme events from 1870 to 1919. Marine heat waves are defined as at least five days of unusually high temperatures for a patch of ocean. Heat waves wreak havoc on ocean ecosystems, leading to seabird starvation, coral bleaching, dying kelp forests, and migration of fish, whales and turtles in search of cooler waters (SN: 1/15/20; SN: 8/10/20). In May 2020, NOAA announced that it was updating its “climate normal” — what the agency uses to put daily weather events in historical context from the average 1981–2010 values to the higher 1991–2020 averages (SN: 5/26/21). This study emphasizes that ocean heat extremes are also now the norm, Van Houston says. “Much of the public discussion now on climate change is about future events, and whether they might happen,” he says. “Extreme heat became common in our ocean in 2014. It’s a documented historical fact, not a future possibility.” A new analysis of monthly sea surface temperatures across the global ocean reveals how more and more patches of ocean saw heat extremes every year. These four decade snapshots show temperature shifts since 1980. Beginning in 2014, more than half of the ocean began to reach extremes hotter than even the most extreme events from 1870 to 1919. From 2013 to 2016, a mass of sweltering water in the eastern Pacific Ocean, known as the Blob, wreaked havoc on marine ecosystems. This illustration shows how unusually hot the waters were in May 2015, with the deepest red representing 3 degrees Celsius above average.