Impact of climate change
Impact of climate change
Different types of natural records have different strengths. 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. (The oldest cores drilled from ocean sediments date back 65 million years, according to The Smithsonian Institution.) Tree records are relatively short but incredibly detailed. 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. 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.
The most recent changes in the climate — since the beginning of the Industrial Revolution — can also be tracked directly. Keeping records 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 advent of satellite technology in the 1970s has provided an explosion of data, covering everything from ice extent at the poles to sea surface temperature to cloud coverage.
How the climate is changing
Taken together, these records have shown that the modern climate is undergoing a swift departure from the patterns of the past.
Before the Industrial Revolution, there were about 280 carbon dioxide molecules for every million molecules in the atmosphere, a measure known as parts per million (ppm). As of 2018, the global average level of CO2 was 407.4 ppm, more than 100 ppm higher than that level has been for the past 800,000 years, according to the National Oceanic and Atmospheric Administration (NOAA). The last time atmospheric carbon reached today’s levels was 3 million years ago, according to NOAA.
The rate of change in today’s atmospheric carbon is also faster than in the past, according to NOAA. The rate of increase was 100 times faster over the past 60 decades 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. And the rate continues to increase. In the 1960s, atmospheric carbon went up by an average of 0.6 ppm a year. In the 2010s, it rose an average of 2.3 ppm per year.
The heat-trapping ability of all that extra carbon has translated to rising global average temperatures. According to NASA’s Goddard Institute for Space Studies (GISS), 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. As with the rate of atmospheric carbon increase, the rate of global temperature increase is also speeding up, according to NASA’s Earth Observatory: Two-thirds of that warming has occurred since 1975.
What are the impacts of climate change?
This warming has translated to changes in Earth ecosystems and environments. Among the most dramatic changes have occured in the Arctic, where sea ice is on the decline. Ice extent lows and record lows have been the new normal since 2002, according to NASA, and studies are finding that even the oldest, multiyear sea ice is thinning rapidly. Scientists now expect the first ice-free Arctic summer sometime between 2040 and 2060.
Glaciers are retreating globally, particularly in the middle latitudes, Mosley-Thompson said. Montana’s Glacier National Park was home to 150 glaciers in 1850. Today, there are only 25. Mosley-Thompson and her team estimate that the last tropical glaciers will disappear within the next decade.
Melting ice and the expansion of ocean waters due to heat have already contributed to sea level rise. According to NOAA, global average sea level has risen 8-9 inches (21-24 centimeters) since 1880. The rate of rise is increasing, from 0.06 inches (1.4 millimeters) per year in the 20th century to 0.14 inches (3.6 mm) per year from 2006-2015. According to NOAA, this sea level rise has translated to a 300% to 900% increase in high-tide flooding in coastal areas in the United States.
Ocean water absorbs carbon dioxide from the atmosphere, which creates a chemical reaction that causes ocean acidification. Global average pH of ocean surface waters has decreased by 0.11 since the Industrial Revolution began, a 30% increase in acidity, according to NOAA’s Pacific Marine Environmental Laboratory. Increasing ocean acidity makes it more difficult for corals to build their carbonate skeletons and for shelled animals such as clams and some types of plankton to survive.
Climate change is even affecting the timing of spring-like weather. The earliest spring (as defined by plant growth and temperatures) on record in the United States was in March 2012. Climate models now suggest that such early springs could be the norm by 2015. But late freezes will likely still occur, creating conditions in which plants could leaf out early and then be damaged by cold temperatures. Climate models also predict the exacerbation of alarming trends in droughts and wildfires thanks to warmer temperatures.
Models are a key tool for climate scientists, said Kathie Dello, North Carolina’s state climatologist. There’s no comparison planet for Earth, Dello said, but models allow scientists to create virtual versions of the planet to test different scenarios. Though the Earth system is complicated, these computer models have proved capable of predicting the future. A 2020 paper in the journal Geophysical Research Letters found that climate model predictions published between the 1970s and 2010 were accurate when compared with the actual warming that occured after publication.