Over this same period, world population increased by 45%, atmospheric CO2 increased by 10%, and the average global surface temperature (as calculated by NASA) increased by 0.9ºF (0.5ºC). found that a principal measure of worldwide vegetation productivity increased by 6.2% between 19.The paper notes that this occurred during a period in which human population increased by 37%, the level of atmospheric CO2 increased by 9%, and the Earth “had two of the warmest decades in the instrumental record.”  attributes this increased productivity to “higher temperatures, longer temperate growing seasons, more rainfall in some previously water-limited areas,” and more sunlight.
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.
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.
By increasing the CO2 level in the greenhouse atmosphere (typical to 600 ppm instead of normal 400 ppm value), the growth for some plants can be stimulated in an important way, with often yield increases up to 20%, especially for tomato, cucumber, strawberry, etc.
* This graph is called the “hockey stick graph” because the curve looks like a hockey stick laid on its side (click on the footnote for a 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).