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 11,700 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 changing 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% probability) to be the result of human activity since the mid-20th century and proceeding at a rate that is unprecedented over 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.
Global Temperature Rise
The planet’s average surface temperature has risen about 2.12 degrees Fahrenheit (1.18 degrees Celsius) since the late 19th century, a change driven largely by increased carbon dioxide emissions into the atmosphere and other human activities. Most of the warming occurred in the past 40 years, with the seven most recent years being the warmest. The years 2016 and 2020 are tied for the warmest year on record.
The ocean has absorbed much of this increased heat, with the top 100 meters (about 328 feet) of ocean showing warming of more than 0.6 degrees Fahrenheit (0.33 degrees Celsius) since 1969.6 Earth stores 90% of the extra energy in the ocean.
Shrinking Ice Sheets
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 279 billion tons of ice per year between 1993 and 2019, while Antarctica lost about 148 billion tons of ice per year.
Glaciers are retreating almost everywhere around the world — including in the Alps, Himalayas, Andes, Rockies, Alaska, and Africa.
Decreased Snow Cover
Satellite observations reveal that the amount of spring snow cover in the Northern Hemisphere has decreased over the past five decades and the snow is melting earlier.
The number of record high-temperature events has been increasing, while the number of record low-temperature events has been decreasing, since 1950.
Since the beginning of the Industrial Revolution, the acidity of surface ocean waters has increased by about 30%.13,14 This increase is the result of humans emitting more carbon dioxide into the atmosphere and hence more being absorbed into the ocean. The ocean has absorbed between 20% and 30% of total anthropogenic carbon dioxide emissions in recent decades (7.2 to 10.8 billion metric tons per year).
Scientists attribute the global warming trend observed since the mid-20th century to the human expansion of the “greenhouse effect”1 — warming that results when the atmosphere traps heat radiating from Earth toward space.
Certain gases in the atmosphere block heat from escaping. Long-lived gases that remain semi-permanently in the atmosphere and do not respond physically or chemically to changes in temperature are described as “forcing” climate change. Gases, such as water vapour, which respond physically or chemically to changes in temperature are seen as “feedbacks.”
- Water vapour. The most abundant greenhouse gas, but importantly, it acts as feedback to the climate. Water vapour increases as the Earth’s atmosphere warms, but so does the possibility of clouds and precipitation, making these some of the most important feedback mechanisms to the greenhouse effect.
- Carbon dioxide (CO2). A minor but very important component of the atmosphere, carbon dioxide is released through natural processes such as respiration and volcano eruptions and through human activities such as deforestation, land-use changes, and burning fossil fuels. Humans have increased atmospheric CO2 concentration by 48% since the Industrial Revolution began. This is the most important long-lived “forcing” of climate change.
- Methane. A hydrocarbon gas is produced both through natural sources and human activities, including the decomposition of wastes in landfills, agriculture, and especially rice cultivation, as well as ruminant digestion and manure management associated with domestic livestock. On a molecule-for-molecule basis, methane is a far more active greenhouse gas than carbon dioxide, but also one which is much less abundant in the atmosphere.
- Nitrous oxide. A powerful greenhouse gas produced by soil cultivation practices, especially the use of commercial and organic fertilizers, fossil fuel combustion, nitric acid production, and biomass burning.
- Chlorofluorocarbons (CFCs). Synthetic compounds entirely of industrial origin are used in a number of applications, but are now largely regulated in production and released to the atmosphere by international agreement for their ability to contribute to the destruction of the ozone layer. They are also greenhouse gases.
Change Will Continue Through This Century and Beyond
Global climate is projected to continue to change over this century and beyond. The magnitude of climate change beyond the next few decades depends primarily on the amount of heat-trapping gases emitted globally, and how sensitive the Earth’s climate is to those emissions.
Temperatures Will Continue to Rise
Because human-induced warming is superimposed on a naturally varying climate, the temperature rise has not been, and will not be, uniform or smooth across the country or over time.
Changes in Precipitation Patterns
Projections of future climate suggest that the recent trend towards increased heavy precipitation events will continue. This trend is projected to occur even in regions where total precipitation is expected to decrease, such as the Southwest of USA
More Droughts and Heat Waves
By the end of this century, what have been once-in-20-year extreme heat days (one-day events) are projected to occur every two or three years over most of the
Sea Level Will Rise 1-8 feet by 2100
Global sea level has risen by about 8 inches since reliable record-keeping began in 1880. It is projected to rise another 1 to 8 feet by 2100. This is the result of added water from melting land ice and the expansion of seawater as it warms.
Arctic Likely to Become Ice-Free
The Arctic Ocean is expected to become essentially ice-free in summer before mid-century.
Some of the most promising ways to mitigate climate change are what we call “natural climate solutions”: the conservation, restoration, and improved management of land, in order to increase carbon storage or avoid greenhouse-gas emissions in landscapes worldwide
. Renewable energies
Changing our main energy sources to clean and renewable energy. Solar, Wind, Geothermal and biomass could be the solution.
- Sustainable transportation
Our transport methods must be aligned with environmental requirements and reduce their carbon footprint. It is essential to rethink our transport methods from the design stage towards eco-friendly transportation.
- Air pollution prevention
Many methods exist to prevent, control and reduce air pollution, in particular by reducing the consumption of fossil fuels, and limiting industrial emissions and waste.
- Waste Management & recycling
The simplest solution to reducing waste is to adapt our production methods to our consumption patterns. The recycling process must also be taken into account in our consumption habits.
- Sea and Ocean preservation
Oceans and seas are the largest storage of greenhouse gases and are an exceptional support system for life on this planet. Limiting overfishing, unsustainable development activities in coastal areas and the consumption of environmentally friendly products is now essential.
- Circular economy
Use the 3 r’s of circular economy (Reduce, Reuse and Recycle) to significantly reduce our waste and avoid unnecessary production of new items.