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Crop Agriculture

About Human-Caused Climate Change 

(Access links and see information below graphic for a background on climate change)

 Atmospheric Carbon Dioxide (CO2) Global Warming Gas Level Over Time: Level as of 5/18/19 is 415.02

(Chart Above from NASA, 2018 at:; can also be seen in NASA link below)

Recommended Offsite Pages (see information below links):

The Keeling Curve Page (Scripps Institute page that shows the current atmospheric level of CO2 )

NASA Climate Change Facts (NASA page that includes comprehensive climate change information)

How Global Warming Warming Causes Cold Snaps (InsideClimate News page)

How Climate Change Has Slowed Ocean Circulation (InsideClimate News page)



Human-caused climate change, including global warming, affects crops, wildfires, snow, and much more. Human-caused global warming is mostly caused by burning fossil fuels (which emits global warming gases such as carbon dioxide [CO2], methane [CH4], and nitrous oxide [N20]), but is also caused, to a lesser extent, by numerous other factors, such as deforestation (this includes clearing land for farming). See this NASA page for global warming information - 16 of the 17 hottest years on record have occurred since 2001 (1998 being the only exception). The information and links on this page provide a good basic understanding of climate change and global warming.

More greenhouse gases than those that would occur naturally in Earth's atmosphere equals a human-caused warmer planet. Solar radiation is mostly shortwave radiation and, as a result, transmits/passes through greenhouse gases, heating the surface of Earth; the heat from Earth produces longwave radiation which the greenhouse gases trap in the atmosphere, warming it. This is a simplified explanation, but explains the basics of the greenhouse effect and global warming. An analogy for the greenhouse effect, is why the air inside of a car with the windows up gets hotter than the air outside. Solar radiation transmit through windows, heating up the inside surfaces of the car; the hot surfaces produce long wavelengths which cannot transmit through the glass, heating the air in the car. Humans must adapt to manage natural resources in a sustainable way. Even with global average temperature increasing, a cold snap in an area can still occur (which may even include a record cold temperature), but is meaningless in the big picture of global warming - recent research suggests that global warming may be contributing to areas of cold air that normally reside to the north moving farther south (and that cold air being replaced by warming air to the south) (Francis et al., 2017), such as the cold snap in the eastern USA that occurred from December 2017 to January 2018.

The most profound and important evidence that supports human-caused global warming is the Keeling Curve. In 1958, Charles David Keeling started recording the amount of CO2 in Earth's atmosphere from the Mauna Loa Observatory on the big island of Hawaii (measurement taken at about 11,400 feet above sea level). From this high and remote location, clean and representative samples of the amount of carbon dioxide in Earth's atmosphere can be taken. Though Mauna Loa is an ideal location, there are other stations in the world where CO2 is measured - the readings from those locations highly correlate with each other and the Keeling Curve at Mauna Loa.

The first graph shows the full Keeling Curve record, from the first measurement in 1958 to 12/29/2017. CO2 amounts change within a year due to the change in amount and vigor of vegetation (including crops and forests; more robust vegetation corresponds to lower CO2 levels). In 2016, CO2 amounts surpassed 400 ppm for the first time in millions of years (amount were higher a few millions years ago due to, essentially, a much different phase of Earth that is not very relevant to today's situation). The second and third graphs show longer term CO2 amounts.

All graphs below are cited from the Scripps Institute of Oceanography website, Keeling Curve page at:



At the long term time scale shown next, fluctuations in Earth's CO2 levels are mainly due to Earth's fluctuating orbit patterns, which affects the amount of solar energy Earth receives and, therefore, ice coverage. CO2 amounts increase as ice coverage decreases (negatively correlated), mainly due to outgassing of CO2 by oceans (when there is less ice, there is more ocean surface and, correspondingly, more CO2 outgassing); the amounts are fairly consistent through time, except for the more recent years when humans have caused increases in CO2.



Francis, J.A., Vavrus, S.J., and J. Cohen. 2017. WIREs Clim Change. 2017, 8:e474. doi: 10.1002/wcc.474.

NASA. 2018. Global Climate Change: Vital Signs of the Planet; Evidence. Website last upated in December, 2018. Cited at: