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.
Global Warming Potential (GWP) is an index to measure of how much infrared thermal radiation a greenhouse gas would absorb over a given time frame after it has been added to the atmosphere. The GWP makes different greenhouse gases comparable with regards to their "effectiveness in causing radiative forcing". It is expressed as a multiple of the radiation that would be absorbed by the same mass of added carbon dioxide,which is taken as a reference gas. Therefore,the GWP is one for CO2. For other gases it depends on how strongly the gas absorbs infrared thermal radiation,how quickly the gas leaves the atmosphere,and the time frame being considered.
Life cycle assessment (LCA),also known as life cycle analysis,is a methodology for assessing environmental impacts associated with all the stages of the life cycle of a commercial product,process,or service. For instance,in the case of a manufactured product,environmental impacts are assessed from raw material extraction and processing (cradle),through the product's manufacture,distribution and use,to the recycling or final disposal of the materials composing it (grave).
Bioenergy is a type of renewable energy that is derived from plants and animal waste. The biomass that is used as input materials consists of recently living organisms,mainly plants. Thus,fossil fuels are not regarded as biomass under this definition. Types of biomass commonly used for bioenergy include wood,food crops such as corn,energy crops and waste from forests,yards,or farms.
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.
The Special Report on Emissions Scenarios (SRES) is a report by the Intergovernmental Panel on Climate Change (IPCC) that was published in 2000. The greenhouse gas emissions scenarios described in the Report have been used to make projections of possible future climate change. The SRES scenarios,as they are often called,were used in the IPCC Third Assessment Report (TAR),published in 2001,and in the IPCC Fourth Assessment Report (AR4),published in 2007. The SRES scenarios were designed to improve upon some aspects of the IS92 scenarios,which had been used in the earlier IPCC Second Assessment Report of 1995. The SRES scenarios are "baseline" scenarios,which means that they do not take into account any current or future measures to limit greenhouse gas (GHG) emissions.
Climate change mitigation is action to limit climate change. This action either reduces emissions of greenhouse gases or removes those gases from the atmosphere. The recent rise in global temperature is mostly due to emissions from burning fossil fuels such as coal,oil,and natural gas. There are various ways how mitigation can reduce emissions. One important way is to switch to sustainable energy sources. Other ways are to conserve energy and to increase efficiency. It is possible to remove carbon dioxide from the atmosphere. This can be done by enlarging forests,restoring wetlands and using other natural and technical processes. The name for these processes is carbon sequestration. Governments and companies have pledged to reduce emissions to prevent dangerous climate change. These pledges are in line with international negotiations to limit warming.
A carbon footprint (or greenhouse gas footprint) is a calculated value or index of the total amount of greenhouse gases that an activity 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.
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.
Biomass,in the context of energy production,is matter from recently living organisms which is used for bioenergy production. Examples include wood,wood residues,energy crops,agricultural residues including straw,and organic waste from industry and households. Wood and wood residues is the largest biomass energy source today. Wood can be used as a fuel directly or processed into pellet fuel or other forms of fuels. Other plants can also be used as fuel,for instance maize,switchgrass,miscanthus and bamboo. The main waste feedstocks are wood waste,agricultural waste,municipal solid waste,and manufacturing waste. Upgrading raw biomass to higher grade fuels can be achieved by different methods,broadly classified as thermal,chemical,or biochemical.
A low-carbon economy (LCE) or decarbonised economy is a concept for a desirable economy which has relatively low greenhouse gas (GHG) emissions per person. 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 even more ambitious target than low-carbon economies are zero-carbon economies with net zero emissions. 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%.
Low-carbon electricity or low-carbon power is electricity produced with substantially lower greenhouse gas emissions over the entire lifecycle than power generation using fossil fuels. The energy transition to low-carbon power is one of the most important actions required to limit climate change.
An economic input-output life-cycle assessment,or EIO-LCA involves the use of aggregate sector-level data to quantify the amount of environmental impact that can be directly attributed to each sector of the economy and how much each sector purchases from other sectors in producing its output. Combining such data sets can enable accounting for long chains,which somewhat alleviates the scoping problem of traditional life-cycle assessments. EIO-LCA analysis traces out the various economic transactions,resource requirements and environmental emissions required for producing a particular product or service.
Greenhouse gases 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).
Atmospheric methane is the methane present in Earth's atmosphere. The concentration of atmospheric methane is increasing due to methane emissions,and is causing climate change. Methane is one of the most potent greenhouse gases. Methane's radiative forcing (RF) of climate is direct,and it is the second largest contributor to human-caused climate forcing in the historical period. Methane is a major source of water vapour in the stratosphere through oxidation;and water vapour adds about 15% to methane's radiative forcing effect. The global warming potential (GWP) for methane is about 84 in terms of its impact over a 20-year timeframe. and 28 in terms of its impact over a 100-year timeframe.
Greenhouse gas emissions are one of the environmental impacts of electricity generation. Measurement of life-cycle greenhouse gas emissions involves calculating the global warming potential of energy sources through life-cycle assessment. These are usually sources of only electrical energy but sometimes sources of heat are evaluated. The findings are presented in units of global warming potential per unit of electrical energy generated by that source. The scale uses the global warming potential unit,the carbon dioxide equivalent,and the unit of electrical energy,the kilowatt hour (kWh). The goal of such assessments is to cover the full life of the source,from material and fuel mining through construction to operation and waste management.
A Representative Concentration Pathway (RCP) is a greenhouse gas concentration trajectory adopted by the IPCC. Four pathways were used for climate modeling and research for the IPCC Fifth Assessment Report (AR5) in 2014. The pathways describe different climate change scenarios,all of which are considered possible depending on the amount of greenhouse gases (GHG) emitted in the years to come. The RCPs –originally RCP2.6,RCP4.5,RCP6,and RCP8.5 –are labelled after a possible range of radiative forcing values in the year 2100. The higher values mean higher greenhouse gas emissions and therefore higher global temperatures and more pronounced effects of climate change. The lower RCP values,on the other hand,are more desirable for humans but require more stringent climate change mitigation efforts to achieve them.
John Richard Barrett is a British academic who is chair in Energy and Climate Policy at the University of Leeds. He is the Director of the Centre for Industrial Energy,Materials and Products (CIE-MAP) and co-director of the UK Energy Research Centre.
