Kaya identity
Encyclopedia
The Kaya identity is an equation relating factors that determine the level of human impact on climate, in the form of emissions of the greenhouse gas
carbon dioxide
. It states that total emission level can be expressed as the product of four inputs: population, GDP per capita, energy use per unit of GDP, carbon emissions per unit of energy consumed. This equation is very simple and tricky, as it can be reduced to only two terms, but it is developed so that the carbon emission calculation becomes easy, as per the available data, or generally in which format the data is available.
The identity is expressed in the form:
whereG is world GDP and g = (G/P) is global per-capita GDP,
E is global primary energy consumption and e=(E/G) is the energy intensity of world GDP,
and f=(F/E) is the carbon intensity of energy.
Extensive variables are uppercase while intensive variables are lowercase.
s in the IPCC
Special Report on Emissions Scenarios
. The scenarios set out a range of assumed conditions for future development of each of the four inputs. Population growth projections are available independently from demographic research; GDP per capita trends are available from economic statistics and econometrics; similarly for energy intensity and emission levels.
The projected carbon emissions can drive carbon cycle
and climate models to predict future CO2 concentration and climate change
.
A 2007 article uses the Kaya Identity in its analysis of recent trends in carbon emissions, and finds:
Greenhouse gas
A greenhouse gas is a gas in an atmosphere that absorbs and emits radiation within the thermal infrared range. This process is the fundamental cause of the greenhouse effect. The primary greenhouse gases in the Earth's atmosphere are water vapor, carbon dioxide, methane, nitrous oxide, and ozone...
carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
. It states that total emission level can be expressed as the product of four inputs: population, GDP per capita, energy use per unit of GDP, carbon emissions per unit of energy consumed. This equation is very simple and tricky, as it can be reduced to only two terms, but it is developed so that the carbon emission calculation becomes easy, as per the available data, or generally in which format the data is available.
Overview
The Kaya identity was developed by Japanese energy economist Yoichi Kaya. It is the subject of his book Environment, Energy, and Economy: strategies for sustainability co-authored with Keiichi Yokobori as the output of the Conference on Global Environment, Energy, and Economic Development (1993 : Tokyo, Japan).The identity is expressed in the form:
where
- F is global CO2 emissions from human sources,
- P is global population,
Extensive variables are uppercase while intensive variables are lowercase.
Use in IPCC reports
The Kaya identity plays a core role in the development of future emissions scenarioScenario
A scenario is a synoptical collage of an event or series of actions and events. In the Commedia dell'arte it was an outline of entrances, exits, and action describing the plot of a play that was literally pinned to the back of the scenery...
s in the IPCC
Intergovernmental Panel on Climate Change
The Intergovernmental Panel on Climate Change is a scientific intergovernmental body which provides comprehensive assessments of current scientific, technical and socio-economic information worldwide about the risk of climate change caused by human activity, its potential environmental and...
Special Report on Emissions Scenarios
Special Report on Emissions Scenarios
The Special Report on Emissions Scenarios was prepared by the Intergovernmental Panel on Climate Change in 2000, based on data developed at the Earth Institute at Columbia University. The emissions scenarios described in the Report have been used to make projections of possible future climate...
. The scenarios set out a range of assumed conditions for future development of each of the four inputs. Population growth projections are available independently from demographic research; GDP per capita trends are available from economic statistics and econometrics; similarly for energy intensity and emission levels.
The projected carbon emissions can drive carbon cycle
Carbon cycle
The carbon cycle is the biogeochemical cycle by which carbon is exchanged among the biosphere, pedosphere, geosphere, hydrosphere, and atmosphere of the Earth...
and climate models to predict future CO2 concentration and climate change
Climate change
Climate change is a significant and lasting change in the statistical distribution of weather patterns over periods ranging from decades to millions of years. It may be a change in average weather conditions or the distribution of events around that average...
.
Use in other scientific analysis
The Kaya identity is reviewed in a 2002 paper.A 2007 article uses the Kaya Identity in its analysis of recent trends in carbon emissions, and finds:
... cessation or reversal of earlier declining trends in the energy intensity of gross domestic product (GDP) (energy/GDP) and the carbon intensity of energy (emissions/energy), coupled with continuing increases in population and per-capita GDP. Nearly constant or slightly increasing trends in the carbon intensity of energy have been recently observed in both developed and developing regions. No region is decarbonizing its energy supply.
External links
- Climate change - what is Kaya's equation
- http://www.worldchanging.com/archives/002952.html
- http://www.computare.org/Support%20documents/Fora%20Input/CCC2006/Sustainable%20Paper%2006_05.htm
- http://www.realclimate.org/index.php?p=164
- Online 'Kaya Calculator'