Climate forcings are the initial drivers of a climate shift. Solar irradiance is one example of a forcing. If the sun generates more light, the Earth will warm.Things that influence the total positive or negative forcing of the earth climate system include:
- Surface reflectivity (albedo)
- Greenhouse gases
- Atmospheric aerosols (volcanic sulfates, industrial output)
Understanding climate forcing is actually easy. Force is generally understood as strength or energy, the cause of motion or change, or active power. This could be a person pushing a shopping cart or an engine that powers a car. For example, gravitational force is how the moons gravity causes the tides to change. Radiative forcing caused by greenhouse gases in our atmosphere keeps the earth from being a frozen ball in space, because the sun provides energy, and the greenhouse gases in our atmosphere trap the heat on earth... a positive forcing.
The National Academy of Sciences, National Research Council, Board on Atmospheric Science and Climate Present:
'Climate Change: Lines of Evidence - How Much Warming?'
To understand the climate forcing, you just add all the components of forcing that are positive and negative and you end up with a view of the total forcing in the climate system of earth.
In our case, the sun provides our heat energy, the Milankovitch forcing is the general regulator of climate forcing over 100k year time scales. That combined with terrestrial components, such as greenhouse gases, aerosols, and changes in land use comprise the major factors that determine climate forcing.
Energy absorption (how much energy we get form the sun) and energy radiation (how much we radiate back out into space) part of the climate system. According the the Stefan Boltzmann Law, we receive on earth 240 W/m2 and we radiate the same back to space.
Earth regulators include thermal inertia of the ocean, land use, and greenhouse gases & aerosols in the atmosphere. These things determine the speed of climate change in combination with the above factors, in general.
Some of the effects are faster and some are slower.
All these parts of the system, once measured and modeled reasonably give you an idea of the amount of forcing each imposes on the climate system. Some forces are positive and others are negative.
Changes in Climate "Forcings"
The following figure shows changes in climate "forcings" or factors that have contributed to climate change since 1750.
These agents can be categorized into three areas: greenhouse gases, other man-made (anthropogenic) forcings, and natural forcings. The greenhouse gases consist of carbon dioxide (CO2), methane (CH4), nitrous oxide (N20) and chlorofluorocarbons (CFCs). Other anthropogenic forcings consist of black carbon (soot, formed by incomplete combustion), reflective aerosols (tiny airborne particles that reflect sunlight back to space), soil or dust, land cover changes, and forced cloud changes. Natural forcings include changes of the sun's energy. Figure is also available in PDF format. (Source: Figure 28 of Hansen et al. 2005. See references below.)
IPCC AR4 Forcing Components
Effective Forcings Employed in Current Climate Simulations
The following figures show effective global climate forcings employed in our current global climate simulations (e.g., Hansen et al. 2007a,b), relative to their values in 1880.
Further Details and Various Future Scenarios to 2100
- Hansen, J., L. Nazarenko, et al. 2005a. Earth's energy imbalance: Confirmation and implications. Science 308, 1431-1435, doi:10.1126/science.1110252. (See also Imbalance webpages).
- Hansen, J., M. Sato, et al. 2005b. Efficacy of climate forcings. J. Geophys. Res., 110, D18104, doi:10.1029/2005/JD005776. (See also Efficacy webpages).
- Hansen, J., et al. 2007a. Dangerous human-made interference with climate: A GISS modelE study. Atmos. Chem. Phys., 7, 2287-2312.
- Hansen, J., et al. 2007b. Climate Dynam., Climate simulations for 1880-2003 with GISS modelE. Climate Dynam., 29, 661-696, doi:10.1007/s00382-007-0255-8.
- 2009 http://www.realclimate.org/index.php/archives/2009/04/yet-more-aerosols-comment-on-shindell-and-faluvegi/
- 2005 Planetary Energy Imbalance Gavin Schmidt
- Aerosols: The Last Frontier? RealClimate Group
- What is a first-order climate forcing? Gavin Schmidt
- 2005 July 6 – Climate sensitivity and aerosol forcings Gavin Schmidt
- 2005/04 RealClimate: Water Vapour Feedback or Forcing
- 2005 January 18 – Global Dimming Gavin Schmidt
- 2005 January 19 – Global Dimming II RealClimate Group, Beate Liepert
- NASA/NCDC/NOAA What are climate forcings?
- NASA/NCDC/NOAA Climate Forcing Data (more hidden data that is always publicly available)
- NASA/NOAA Aerosol Indirect Effect on Clouds: Climate Implications - 2003, 2000
- NASA/NCDC/NOAA Causes of Climate Change Over the Past 1000 Years Published July 14, 2000 Science, 289: 270-277.
- NASA/NOAA Aerosol Climate Forcing - 1997 Patricia Quinn & Timothy Bates Derek Coffman, Drew Hamilton, Jim Johnson, & Theresa Miller
- NASA: Water Vapor Confirmed as Major Player in Climate Change - Nov. 2008
- RealClimate: Water vapour: feedback or forcing?
- 2005 July 15 RealClimate: The lure of solar forcing Gavin Schmidt
- Wikipedia: The Stefan Boltzmann Law
- Stefan-Boltzmann Constant
- 11ºC warming, climate crisis in 10 years? () ()
- Climate sensitivity and aerosol forcings
- Natural Variability and Climate Sensitivity
- Richard Lindzen's HoL testimony
- Climate sensitivity: Plus ça change…
- Runaway tipping points of no return () ()
- Climate Feedbacks
- The CO2 problem in 6 easy steps
- Climate Insensitivity
- The certainty of uncertainty
- Target CO2 () ()
- Simple Question, Simple Answer… Not () () () () ()
- Global Dimming? () ()
- Global Dimming II () ()
- Pollution-Climate Connections () ()
- Global Dimming may have a brighter future () ()
- Climate sensitivity and aerosol forcings
- An Aerosol Tour de Forcing
- Global Dimming and climate models
- Current volcanic activity and climate?
- Aerosols: The Last Frontier? () ()
- Ozone impacts on climate change
- Perspectives from China
- Global dimming and global warming
- Aerosols, Chemistry and Climate