A little goes a long way:
carbon dioxide & methane in the atmosphere.
"The few things we do know about the response of the Earth to our presence are deeply disturbing. Even if we stopped immediately all seizing of Gaia's land and water for food and fuel production and stopped poisoning the air, it would take the Earth more than a thousand years to recover from the damage we have already done and it may be too late for even this drastic step to save us."
James Lovelock The Revenge of Gaia, p. 6.
By 2015 the level of carbon dioxide that was measured in the atmosphere was at a level not seen since between 800,000 and ten to fifteen million years ago in the Miocene epoch. Other experts say, not since the Oligocene epoch 23 million years ago.
"Raising atmospheric concentrations of CO2 to 0.04 percent may not seem like much but it has been enough to raise the world's annual average temperature by a total of 0.8 degree Celsius so far. More warming is in store, thanks to the lag between CO2 emissions and the extra heat each molecule will trap over time . . . "
"CO2 Levels for February Eclipsed Prehistoric Highs: Global warming is headed back to the future as the CO2 level reaches a new high"
By David Biello
Scientific American, March 5, 2015.
• 400 parts per million is the current reading of CO2 in the air [off the chart below].
Weekly trends in carbon dioxide concentration levels in the atmosphere.
• the average global temperature has increased by 1.5 degrees since 1880 (an average).
"The time of irreversible change may be so close that it would be unwise to rely on international agreement to save civilization from the consequences of global heating."
Lovelock, p. 13.
Climate change is a global issue and is being driven by enhanced atmospheric greenhouse gas levels. The levels of these gases have continued to increase as shown by measurements of carbon dioxide (CO2) at Mace Head on the west coast of Ireland.
These observations are replicated at other sites around the world. Current atmospheric levels now exceed by far the natural range over the last 800,000 years.
"Climatologists now think that we are perilously close to the threshold beyond which adverse change sets in; that is change that is, on a human time scale, irreversible."
Lovelock, p. 46.
For up-to-date information see–
Compare the above graphic to the MET –meteorological office– in the United Kingdom:
The overwhelming majority of scientists agree that this is due to rising concentrations of heat-trapping greenhouse gases in the atmosphere caused by human activities.
Spencer Weart | Gale Christianson | James Hansen | Contemporary | Robert Musil | David Archer | Gavin Schmidt | data
Hansen – 06 | Current findings | abrupt climate change | biodiversity and climate | Recent findings