Scientists now expect the first ice-free Arctic summer sometime between 20. Summer 2020 was one of the worst years ever for summer sea ice extent, with only one year on record – 2012 – exhibiting a lower ice extent. Record-breaking ice extent lows have been the new normal since 2002, according to NASA (opens in new tab), and studies are finding that even the oldest, multiyear sea ice is thinning rapidly. Some of the most dramatic changes have occurred in the Arctic, where sea ice is on the decline. This warming has caused changes in Earth ecosystems and environments. As with the rate of atmospheric carbon increase, the rate of global temperature increase is also speeding up, according to NASA's Earth Observatory (opens in new tab): Two-thirds of the warming that’s taken place since 1880 has occurred since 1975. According to NASA's Goddard Institute for Space Studies (GISS) (opens in new tab), Earth's average temperature has risen by just over 2 degrees Fahrenheit (1 degree Celsius) since 1880, a measurement accurate to within a tenth of a degree Fahrenheit. The heat-trapping ability of all that extra carbon has translated to rising global average temperatures. In the 2010s, it rose by an average of 2.3 ppm per year. In the 1960s, atmospheric carbon went up by an average of 0.6 ppm a year. The rate of increase was 100 times faster over the past 60 years than any time in the last million years or so - a period that saw eight major climate flip-flops between glacial cycles, in which ice expanded from the poles into the middle latitudes, and interglacial cycles, in which the ice retreated to where it is today. The rate of change in today's atmospheric carbon is also faster than in the past, according to NOAA. The last time atmospheric carbon reached today's levels was 3 million years ago, according to NOAA. As of 2021, the global average level of CO2 was 419 ppm - more than 100 ppm higher than the level has been in the last 800,000 years, and up 6.5 ppm from 2020, according to the National Oceanic and Atmospheric Administration (NOAA) (opens in new tab). Taken together, these records show that the modern climate is undergoing a swift departure from the patterns of the past.īefore the Industrial Revolution, there were about 280 carbon dioxide molecules for every million molecules in the atmosphere, or 280 parts per million (ppm). (Image credit: Shutterstock) (opens in new tab) How is the climate changing? But climate change also causes seasonal periods of extreme cold. Overall, the Earth is warming up because of human-caused climate change. The advent of satellite technology in the 1970s provided an explosion of data, covering everything from ice extent at the poles to sea surface temperature to cloud coverage. Record-keeping of things like land temperature began to improve in the late 1800s, and ship captains began to keep a wealth of ocean-based weather data in their logs. The most recent changes in the climate - since the beginning of the Industrial Revolution - have also been tracked directly. As the ice gets older and more compressed, the record can become fuzzy, Mosley-Thompson said, but newer ice can provide a year-by-year look at what the climate was doing. And ice can be chock-full of information: Not only do glaciers capture atmospheric gases in the form of air bubbles, they trap dust and other sediments, pollen grain, volcanic ash and more. (The oldest cores drilled from ocean sediments date back 65 million years, according to The Smithsonian Institution (opens in new tab).) Tree records are relatively short but incredibly detailed. Ocean sediments don't carry season-by-season or even year-by-year levels of detail, but they can provide blurrier pictures of climate dating back millions of years, Mosley-Thompson told Live Science. Different types of natural records can reveal different clues about the climate of the past.
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