Earth’s climate has changed throughout history. Just in the last 650,000 years there have been seven cycles of glacial advance and retreat, with the abrupt end of the last ice age about 7,000 years ago marking the beginning of the modern climate era — and of human civilization. Most of these climate changes are attributed to very small variations in Earth’s orbit that change the amount of solar energy our planet receives.
The current warming trend is of particular significance because most of it is extremely likely (greater than 95 percent probability) to be the result of human activity since the mid-20thcentury and proceeding at a rate that is unprecedented over decades to millennia.1
Earth-orbiting satellites and other technological advances have enabled scientists to see the big picture, collecting many different types of information about our planet and its climate on a global scale. This body of data, collected over many years, reveals the signals of a changing climate.
The heat-trapping nature of carbon dioxide and other gases was demonstrated in the mid-19th century.2 Their ability to affect the transfer of infrared energy through the atmosphere is the scientific basis of many instruments flown by NASA. There is no question that increased levels of greenhouse gases must cause the Earth to warm in response.
Ice cores drawn from Greenland, Antarctica, and tropical mountain glaciers show that the Earth’s climate responds to changes in greenhouse gas levels. Ancient evidence can also be found in tree rings, ocean sediments, coral reefs, and layers of sedimentary rocks. This ancient, or paleoclimate, evidence reveals that current warming is occurring roughly ten times faster than the average rate of ice-age-recovery warming.
The planet’s average surface temperature has risen about 1.62 degrees Fahrenheit (0.9 degrees Celsius) since the late 19th century, a change driven largely by increased carbon dioxide and other human-made emissions into the atmosphere.5 Most of the warming occurred in the past 35 years, with the five warmest years on record taking place since 2010. Not only was 2016 the warmest year on record, but eight of the 12 months that make up the year — from January through September, with the exception of June — were the warmest on record for those respective months.
The oceans have absorbed much of this increased heat, with the top 700 meters (about 2,300 feet) of ocean showing warming of 0.302 degrees Fahrenheit since 1969
The Greenland and Antarctic ice sheets have decreased in mass. Data from NASA’s Gravity Recovery and Climate Experiment show Greenland lost an average of 281 billion tons of ice per year between 1993 and 2016, while Antarctica lost about 119 billion tons during the same time period. The rate of Antarctica ice mass loss has tripled in the last decade
Glaciers are retreating almost everywhere around the world — including in the Alps, Himalayas, Andes, Rockies, Alaska and Africa
Satellite observations reveal that the amount of spring snow cover in the Northern Hemisphere has decreased over the past five decades and that the snow is melting earlier
Global sea level rose about 8 inches in the last century. The rate in the last two decades, however, is nearly double that of the last century
Both the extent and thickness of Arctic sea ice has declined rapidly over the last several decades
The number of record high temperature events in the United States has been increasing, while the number of record low temperature events has been decreasing, since 1950. The U.S. has also witnessed increasing numbers of intense rainfall events.
Tropical cyclones have grown more sluggish since the mid-20th century, a new study says.
A study published in the journal Nature on Wednesday, June 6, says that hurricanes are lingering in one place for longer.
The study determined this by focusing on the “translation speed.”
The translation speed measures how quickly a storm is moving over an area, for example from the Florida Keys to the Florida Panhandle.
Harvey is seen in the Gulf of Mexico in this satellite image. (Photo/NASA)
To analyze the changes in translation speeds, the researchers tapped into a global data set on past tropical storms. The data include estimates of the latitude and longitude of each named storm’s center at six-hour intervals.
The researchers were able to measure how quickly the storm moved across the landscape. They were then able to calculate the average speeds of the storms from year to year.
The study found that between 1949 and 2016, tropical cyclone translation speeds declined 10 percent worldwide.
While more sluggish storms may sound less dangerous, these slower-moving storms may actually be more deadly, according to the study.
For instance, Hurricane Harvey crawled over Texas in August 2017 dumped more than 30 inches of rain in two days and nearly 50 inches over four days in some areas.
A Harris County report released on Monday, June 4, found that Harvey’s rainfall exceeded every known flooding event in American history since 1899.
Harvey demonstrates the devastating impacts that lingering hurricanes can have on impacted areas. These lingering storms will likely occur more often as the Earth’s atmosphere warms.