The scientific community has been investigating the causes of climate change for decades. After thousands of studies, it came to a consensus, where it is "unequivocal that human influence has warmed the atmosphere, ocean and land since pre-industrial times." This consensus is supported by around 200 scientific organizations worldwide, The dominant role in this climate change has been played by the direct emissions of carbon dioxide from the burning of fossil fuels. Indirect CO2 emissions from land use change, and the emissions of methane, nitrous oxide and other greenhouse gases play major supporting roles.
The greenhouse effect occurs when greenhouse gases in a planet's atmosphere insulate the planet from losing heat to space, raising its surface temperature. Surface heating can happen from an internal heat source as in the case of Jupiter, or from its host star as in the case of the Earth. In the case of Earth, the Sun emits shortwave radiation (sunlight) that passes through greenhouse gases to heat the Earth's surface. In response, the Earth's surface emits longwave radiation (heat) that is mostly absorbed by greenhouse gases. That heat absorption reduces the rate at which the Earth can cool off in response to being warmed by the Sun. Adding to greenhouse gases further reduces the rate a planet emits radiation to space, raising its average surface temperature.
An emission intensity is the emission rate of a given pollutant relative to the intensity of a specific activity, or an industrial production process; for example grams of carbon dioxide released per megajoule of energy produced, or the ratio of greenhouse gas emissions produced to gross domestic product (GDP). Emission intensities are used to derive estimates of air pollutant or greenhouse gas emissions based on the amount of fuel combusted, the number of animals in animal husbandry, on industrial production levels, distances traveled or similar activity data. Emission intensities may also be used to compare the environmental impact of different fuels or activities. In some case the related terms emission factor and carbon intensity are used interchangeably. The jargon used can be different, for different fields/industrial sectors; normally the term "carbon" excludes other pollutants, such as particulate emissions. One commonly used figure is carbon intensity per kilowatt-hour (CIPK), which is used to compare emissions from different sources of electrical power.
Climate change mitigation is action to limit the greenhouse gases in the atmosphere that cause climate change. Greenhouse gas emissions are primarily caused by people burning fossil fuels such as coal, oil, and natural gas. Phasing out fossil fuel use can happen by conserving energy and replacing fossil fuels with clean energy sources such as wind, hydro, solar, and nuclear power. Secondary mitigation strategies include changes to land use and removing carbon dioxide (CO2) from the atmosphere. Governments have pledged to reduce greenhouse gas emissions, but actions to date are insufficient to avoid dangerous levels of climate change.
A carbon footprint (or greenhouse gas footprint) is a calculated value or index that makes it possible to compare the total amount of greenhouse gases that an activity, product, company or country adds to the atmosphere. Carbon footprints are usually reported in tonnes of emissions (CO2-equivalent) per unit of comparison. Such units can be for example tonnes CO2-eq per year, per kilogram of protein for consumption, per kilometer travelled, per piece of clothing and so forth. A product's carbon footprint includes the emissions for the entire life cycle. These run from the production along the supply chain to its final consumption and disposal.
Food miles is the distance food is transported from the time of its making until it reaches the consumer. Food miles are one factor used when testing the environmental impact of food, such as the carbon footprint of the food.
Carbon accounting is a framework of methods to measure and track how much greenhouse gas (GHG) an organization emits. It can also be used to track projects or actions to reduce emissions in sectors such as forestry or renewable energy. Corporations, cities and other groups use these techniques to help limit climate change. Organizations will often set an emissions baseline, create targets for reducing emissions, and track progress towards them. The accounting methods enable them to do this in a more consistent and transparent manner.
A low-carbon economy (LCE) is an economy which absorbs as much greenhouse gas as it emits. Greenhouse gas (GHG) emissions due to human activity are the dominant cause of observed climate change since the mid-20th century. There are many strategies and approaches for moving to a low-carbon economy, such as encouraging renewable energy transition, efficient energy use, energy conservation, electrification of transportation, carbon capture and storage, climate-smart agriculture. An example are zero-carbon cities.
Greenhouse gas (GHG) emissions from human activities intensify the greenhouse effect. This contributes to climate change. Carbon dioxide, from burning fossil fuels such as coal, oil, and natural gas, is one of the most important factors in causing climate change. The largest emitters are China followed by the United States. The United States has higher emissions per capita. The main producers fueling the emissions globally are large oil and gas companies. Emissions from human activities have increased atmospheric carbon dioxide by about 50% over pre-industrial levels. The growing levels of emissions have varied, but have been consistent among all greenhouse gases. Emissions in the 2010s averaged 56 billion tons a year, higher than any decade before. Total cumulative emissions from 1870 to 2017 were 425±20 GtC from fossil fuels and industry, and 180±60 GtC from land use change. Land-use change, such as deforestation, caused about 31% of cumulative emissions over 1870–2017, coal 32%, oil 25%, and gas 10%.
The United States produced 5.2 billion metric tons of carbon dioxide equivalent greenhouse gas (GHG) emissions in 2020, the second largest in the world after greenhouse gas emissions by China and among the countries with the highest greenhouse gas emissions per person. In 2019 China is estimated to have emitted 27% of world GHG, followed by the United States with 11%, then India with 6.6%. In total the United States has emitted a quarter of world GHG, more than any other country. Annual emissions are over 15 tons per person and, amongst the top eight emitters, is the highest country by greenhouse gas emissions per person. However, the IEA estimates that the richest decile in the US emits over 55 tonnes of CO2 per capita each year. Because coal-fired power stations are gradually shutting down, in the 2010s emissions from electricity generation fell to second place behind transportation which is now the largest single source. In 2020, 27% of the GHG emissions of the United States were from transportation, 25% from electricity, 24% from industry, 13% from commercial and residential buildings and 11% from agriculture. In 2021, the electric power sector was the second largest source of U.S. greenhouse gas emissions, accounting for 25% of the U.S. total. These greenhouse gas emissions are contributing to climate change in the United States, as well as worldwide.
Livestock's Long Shadow: Environmental Issues and Options is a United Nations report, released by the Food and Agriculture Organization (FAO) of the United Nations on 29 November 2006, that "aims to assess the full impact of the livestock sector on environmental problems, along with potential technical and policy approaches to mitigation". It stated that livestock accounts for 18% of anthropogenic greenhouse gas emissions, a figure which FAO changed to 14.5% in its 2013 study Tackling climate change through livestock.
A low-carbon diet is any diet that results in lower greenhouse gas emissions. Choosing a low carbon diet is one facet of developing sustainable diets which increase the long-term sustainability of humanity. Major tenets of a low-carbon diet include eating a plant-based diet, and in particular little or no beef and dairy. Low-carbon diets differ around the world in taste, style, and the frequency they are eaten. Asian countries like India and China feature vegetarian and vegan meals as staples in their diets. In contrast, Europe and North America rely on animal products for their Western diets.
Greenhouse gases (GHGs) are the gases in the atmosphere that raise the surface temperature of planets such as the Earth. What distinguishes them from other gases is that they absorb the wavelengths of radiation that a planet emits, resulting in the greenhouse effect. The Earth is warmed by sunlight, causing its surface to radiate heat, which is then mostly absorbed by greenhouse gases. Without greenhouse gases in the atmosphere, the average temperature of Earth's surface would be about −18 °C (0 °F), rather than the present average of 15 °C (59 °F).
In 2021, net greenhouse gas (GHG) emissions in the United Kingdom (UK) were 427 million tonnes (Mt) carbon dioxide equivalent, 80% of which was carbon dioxide itself. Emissions increased by 5% in 2021 with the easing of COVID-19 restrictions, primarily due to the extra road transport. The UK has over time emitted about 3% of the world total human caused CO2, with a current rate under 1%, although the population is less than 1%.
Individual action on climate change can include personal choices in many areas, such as diet, travel, household energy use, consumption of goods and services, and family size. Individuals can also engage in local and political advocacy around issues of climate change. People who wish to reduce their carbon footprint, can take "high-impact" actions, such as avoiding frequent flying and petrol fuelled cars, eating mainly a plant-based diet, having fewer children, using clothes and electrical products for longer, and electrifying homes. Avoiding meat and dairy foods has been called "the single biggest way" an individual can reduce their environmental impact. Excessive consumption is more to blame for climate change than population increase. High consumption lifestyles have a greater environmental impact, with the richest 10% of people emitting about half the total lifestyle emissions.
Increasing methane emissions are a major contributor to the rising concentration of greenhouse gases in Earth's atmosphere, and are responsible for up to one-third of near-term global heating. During 2019, about 60% of methane released globally was from human activities, while natural sources contributed about 40%. Reducing methane emissions by capturing and utilizing the gas can produce simultaneous environmental and economic benefits.
Greenhouse gas emissionsbyRussia are mostly from fossil gas, oil and coal. Russia emits 2 or 3 billion tonnes CO2eq of greenhouse gases each year; about 4% of world emissions. Annual carbon dioxide emissions alone are about 12 tons per person, more than double the world average. Cutting greenhouse gas emissions, and therefore air pollution in Russia, would have health benefits greater than the cost. The country is the world's biggest methane emitter, and 4 billion dollars worth of methane was estimated to leak in 2019/20.
This article documents events, research findings, scientific and technological advances, and human actions to measure, predict, mitigate, and adapt to the effects of global warming and climate change—during the year 2019.
How Bad Are Bananas? The Carbon Footprint of Everything is a 2010 non-fiction book by Mike Berners-Lee. The book details the carbon footprint of a wide range of activities and helps guide people towards less carbon-costly lifestyle options.
