as “an increase in the average temperature of the Earth’s atmosphere,” either by “human industry and agriculture” or by natural causes like the Earth has “experienced numerous” times “through its history.” * Some writers use the phrases “global warming” and “climate change” to mean temperature changes strictly caused by human activity.   Other writers use adjectives such as “man-made” and “anthropogenic” to distinguish between human and non-human causes.  (“Anthropogenic” means “of human origin,” and “AGW” stands for “anthropogenic global warming.”) * Just Facts’ Standards of Credibility require the use of “language that is precise and unambiguous.” Hence, when human causes are stated or implied, this research uses terms like “man-made” and “human-induced.” * The greenhouse effect is a warming effect caused by certain gases that retain heat from sunlight. Without such gases, the average surface temperature of the Earth would be below freezing, and as explained by the , “life, as we know it, would not exist.” The global warming debate is centered upon whether added greenhouse gases released by human activity will overheat the Earth and cause harmful effects. * Human activities currently release about 37 billion metric tons of CO2 per year, which equates to about 5% of natural CO2 emissions.Natural processes absorb the equivalent of all natural emissions plus about 57% of man-made emissions, leaving an additional 16 billion metric tons of CO2 in the atmosphere each year. † In permafrost regions, perennial snow accumulations trap air bubbles that leave records of past airborne CO2 concentrations,   and because regional CO2 concentrations vary by less than 10 parts per million over the Earth, these local records are globally representative.  * Instruments located on satellites can measure certain properties of oxygen that vary with temperature.For instance, the sea level in the Indian Ocean is about 330 feet below the worldwide average, while the sea level in Ireland is about 200 feet above average.Such variations are caused by gravity, winds, and currents; and the practical effects of these phenomena are dynamic.
The second largest influence is calculated to be the melting of glaciers and mountain icecaps. Per a 2010 paper in * Worldwide, sea level is not evenly distributed like it is in small bodies of water such as lakes.do not allow any observational assessment” because many variables are involved, and “it is not possible …to insure that only one variable is changing.” found that during 1973-2007, humidity increased in the lowest part of Earth’s atmosphere but decreased at higher altitudes, implying that the “long-term water vapor feedback is negative—that it would reduce rather than amplify” the warming effect of CO2.* This graph is called the “hockey stick graph” because the curve looks like a hockey stick laid on its side (click on footnote for graphic illustration). The red part of the curve represents modern instrument-measured surface temperatures, the blue represents proxy data, the black line is a smoothed average of the proxy data, and the gray represents the margin of error with 95% confidence.  * This graph has been the subject of disputes in scientific journals,  congressional hearings,  and legal proceedings including a Freedom of Information Act lawsuit.  Just Facts presently does not have the resources to conclusively assess all the competing claims on this issue, but the facts we have verified are as follows: medieval warmth,” and shows the following graph of temperature changes for the Northern Hemisphere over the past 1,300 years.This graph, which is called a “spaghetti graph,” is constructed with data from 12 proxy studies spliced with instrument-measured surface temperatures (the dark black line): * The fifth IPCC report (2013) states that challenges persist in reconstructing temperatures before the time of the instrumental record “due to limitations of spatial sampling, uncertainties in individual proxy records and challenges associated with the statistical methods used to calibrate and integrate multi-proxy information.” This report contains the following spaghetti graphs of proxy studies spliced with instrument-measured surface temperatures (the black lines): * In 2009, an unknown individual(s) released more than 1,000 emails (many dealing with proxy studies) from the University of East Anglia’s Climatic Research Unit (CRU).
The following map shows these productivity changes, with green signifying higher vegetation productivity and red lower: Plants need water, light, warmth, nutrition and CO2 to grow.