Many climate change impacts have been observed in the first decades of the 21st century, with 2024 the warmest on record at +1.60°C (2.88°F) since regular tracking began in 1850. Additional warming will increase these impacts and can trigger tipping points, such as melting all of the Greenland ice sheet. Under the 2015 Paris Agreement, nations collectively agreed to keep warming "well under 2°C". However, with pledges made under the Agreement, global warming would still reach about 2.8°C (5.0°F) by the end of the century.
A carbon credit is a tradable instrument (typically a virtual certificate) that conveys a claim to have avoided greenhouse gas (GHG) emissions or to have enhanced removal of GHG from the atmosphere. One carbon credit represents the avoided or enhanced removal of one metric ton of carbon dioxide or its carbon dioxide-equivalent (CO2e).
Carbon offsetting is the practice of using carbon credits to offset or counter an entity's greenhouse gas inventory emissions in line with reporting programs or institutional emissions targets/goals. Carbon credit trading mechanisms (i.e., crediting programs), enable project developers to implement projects that mitigate GHGs and receive carbon credits which can be sold to interested buyers who may use the credits to claim they have offset their inventory GHG emissions. Similar to "offsetting", carbon credits that are permitted as compliance instruments within regulatory compliance markets (e.g., The European Union Emission Trading Scheme or the California Cap-n-Trade program) can be used by regulated entities to report lower emissions and achieve compliance status (with limitations around their use that vary by compliance program). Aside from "offsetting", carbon credits can also be used to make contributions toward global net zero GHG-level targets. It is an individual buyer's choice how to use, or "retire", the carbon credit.
Projects entail mitigation actions that avoid or enhance the removal of GHG emissions. Projects are implemented in line with the standards of crediting programs, including their methodologies, rules, and requirements. Methodologies are approved for each specific project type (e.g., tree planting, mangrove restoration, early retirement of coal powerplants). Provided a project fulfills all of the requirements and provisions of a crediting program, it will be issued credits that can be sold to buyers. Each crediting program typically has its own carbon credit 'label' such as CDM's Certified Emission Reductions (CERs), Article 6.4 Mechanism Emission Reductions (A6.4ERs), VCS' Verified Emission Reductions (VERs), ACR's Emission Reduction Tonnes, Climate Action Reserves' Climate Reserve Tonnes (CRTs), etc. (Full article...)
An image of the Earth's cloud cover, which is the amount of sky obscured by clouds, based largely on observations from NASA's Moderate Resolution Imaging Spectroradiometer (MODIS) on board the Terra satellite. Clouds play multiple critical roles in the climate system. In particular, being bright objects in the visible part of sunlight, they efficiently reflect light to space and thus contribute to the cooling of the planet.
Cynthia E. Rosenzweig at Goddard Institute for Space Studies, New York.
Cynthia E. Rosenzweig (née Ropes) (born c. 1958) is an American agronomist and climatologist at NASAGoddard Institute for Space Studies, located at Columbia University, "who helped pioneer the study of climate change and agriculture." She is an adjunct senior research scientist at the Columbia Climate School and has over 300 publications, over 80 peer-reviewed articles, has authored or edited eight books. She has also served in many different organizations working to develop plans to manage climate change, at the global level with the IPCC as well as in New York City after Hurricane Sandy. (Full article...)
Image 4The rate of global tree cover loss has approximately doubled since 2001, to an annual loss approaching an area the size of Italy. (from Causes of climate change)
Image 5Energy flows between space, the atmosphere, and Earth's surface. Rising greenhouse gas levels are contributing to an energy imbalance. (from Causes of climate change)
Image 6Meat from cattle and sheep have the highest emissions intensity of any agricultural commodity. (from Causes of climate change)
Image 7Sea ice reflects 50% to 70% of incoming sunlight, while the ocean, being darker, reflects only 6%. As an area of sea ice melts and exposes more ocean, more heat is absorbed by the ocean, raising temperatures that melt still more ice. This is a positive feedback process. (from Causes of climate change)
Image 8Top panel: Observed global average temperature change (1870— ).Bottom panel: Data from the Fourth National Climate Assessment is merged for display on the same scale to emphasize relative strengths of forces affecting temperature change. Human-caused forces have increasingly dominated. (from Causes of climate change)
Image 9Schematic drawing of Earth's excess heat inventory and energy imbalance for two recent time periods (from Earth's energy budget)
Image 10Human fingerprints for global warming (summary of observational evidence that human carbon dioxide emissions are causing the climate to warm). (from Causes of climate change)
Image 11CO2 reduces the flux of thermal radiation emitted to space (causing the large dip near 667 cm−1), thereby contributing to the greenhouse effect. (from Carbon dioxide in the atmosphere of Earth)
Image 15Annual CO2 flows from anthropogenic sources (left) into Earth's atmosphere, land, and ocean sinks (right) since year 1960. Units in equivalent gigatonnes carbon per year. (from Carbon dioxide in the atmosphere of Earth)
Image 16The rising accumulation of energy in the oceanic, land, ice, and atmospheric components of Earth's climate system since 1960 (from Earth's energy budget)
Image 17Observed temperature vs the 1850–1900 average used by the IPCC as a pre-industrial baseline. The primary driver for increased global temperatures in the industrial era is human activity, with natural forces adding variability. (from Causes of climate change)
Image 19Scientific consensus on causation:Academic studies of scientific agreement on human-caused global warming among climate experts (2010–2015) reflect that the level of consensus correlates with expertise in climate science. A 2019 study found scientific consensus to be at 100%, and a 2021 study concluded that consensus exceeded 99%. Another 2021 study found that 98.7% of climate experts indicated that the Earth is getting warmer mostly because of human activity. (from History of climate change science)
Image 22Earth's energy balance and imbalance, showing where the excess energy goes: Outgoing radiation is decreasing owing to increasing greenhouse gases in the atmosphere, leading to Earth's energy imbalance of about 460 TW. The percentage going into each domain of the climate system is also indicated. (from Earth's energy budget)
Image 24Global average temperatures show that the Medieval Warm Period was not a planet-wide phenomenon, and that the Little Ice Age was not a distinct planet-wide time period but rather the end of a long temperature decline that preceded recent global warming. (from Temperature record of the last 2,000 years)
Image 25Earth's energy budget (in W/m2) determines the climate. It is the balance of incoming and outgoing radiation and can be measured by satellites. The Earth's energy imbalance is the "net absorbed" energy amount. (from Earth's energy budget)
Image 26Greenhouse gases allow sunlight to pass through the atmosphere, heating the planet, but then absorb and redirect the infrared radiation (heat) the planet emits. (from Carbon dioxide in the atmosphere of Earth)
Image 27CO2 sources and sinks since 1880. While there is little debate that excess carbon dioxide in the industrial era has mostly come from burning fossil fuels, the future strength of land and ocean carbon sinks is an area of study. (from Causes of climate change)
Image 30Since the 1980s, global average surface temperatures during a given decade have almost always been higher than the average temperature in the preceding decade. (from History of climate change science)
Image 32Extreme event attribution methods generally involve applying climate change models to scenarios in both the "real" world that is experiencing global warming, and a simulated world that does not suffer the drivers of global warming. Differences between the results of the two processes—especially the frequency, intensity and impacts of extreme weather events—are then analyzed to arrive at the attribution result. (from History of climate change science)
Image 33Mean temperature anomalies during the period 1965 to 1975 with respect to the average temperatures from 1937 to 1946. This dataset was not available at the time. (from History of climate change science)
Image 37CO2 concentrations over the last 800,000 years as measured from ice cores (blue/green) and directly (black) (from Causes of climate change)
Image 38Earth's energy imbalance has increased in the 21st century, reaching values twice that of prior estimates from the IPCC. The ability to observe this imbalance is deteriorating because satellites are being decommissioned. (from Earth's energy budget)
Image 42Brown bars indicate drivers that increase global warming, and blue bars indicate those that decrease global warming. Future global warming potential for long lived drivers like carbon dioxide emissions is not represented. (from Causes of climate change)
Image 45Erratics, boulders deposited by glaciers far from any existing glaciers, led geologists to the conclusion that climate had changed in the past. (from History of climate change science)
Image 46Over 400,000 years of ice core data: Graph of CO2 (green), reconstructed temperature (blue) and dust (red) from the Vostok ice core (from Carbon dioxide in the atmosphere of Earth)
Image 47The growth in Earth's energy imbalance from satellite and in situ measurements (2005–2019). A rate of +1.0W/m2 summed over the planet's surface equates to a continuous heat uptake of about 500terawatts (~0.3% of the incident solar radiation). (from Earth's energy budget)
Image 48A Sankey diagram illustrating a balanced example of Earth's energy budget. Line thickness is linearly proportional to relative amount of energy. (from Earth's energy budget)
Image 49The impact of the greenhouse effect on climate was presented to the public early in the 20th century, as succinctly described in this 1912 Popular Mechanics article. (from History of climate change science)
Image 50Modeled simulation of the effect of various factors (including GHGs, Solar irradiance) singly and in combination, showing in particular that solar activity produces a small and nearly uniform warming, unlike what is observed. (from History of climate change science)
A view of Sand Mountain campground from the side of Sand Mountain at Little Sahara Recreation Area in Utah. The Little Sahara sand dunes are remnants of a large river delta formed by the Sevier River from about 12,500 to 20,000 years ago. The river emptied into ancient Lake Bonneville near the present day mouth of Leamington Canyon. After Lake Bonneville receded, winds transported the sand from the river delta to the current location. The dunes are still moving 5 to 9 feet (1.5 to 3 m) per year. The area is home to typical Great Basin desert wildlife including mule deer, pronghorn antelope, snakes, lizards and birds of prey. Great horned owls make their home among juniper trees in the Rockwell Natural Area.
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