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I'll retract my sentence at the beginning of question 1. What I meant was, greenhouse gas concentrations have been increasing since the beginning of the indust

I'll retract my sentence at the beginning of question 1. What I meant was, greenhouse gas concentrations have been increasing since the beginning of the industrial revolution in 1750. I can cite this here: http://en.wikipedia.org/wiki/Greenhouse_gas#Changes_since_the_Industrial_Revolution http://en.wikipedia.org/wiki/Greenhouse_gas#Changes_since_th... and here: http://www.epa.gov/climatechange/pdfs/CI-greenhouse-gases-2014.pdf http://www.epa.gov/climatechange/pdfs/CI-greenhouse-gases-20... But I don't think your response answers my question. The middle 18th century seems to be the beginning of a natural shift in CO2 concentrations, according to figure 1 here: http://www.epa.gov/climatechange/pdfs/CI-greenhouse-gases-2014.pdf http://www.epa.gov/climatechange/pdfs/CI-greenhouse-gases-20... In that figure, we see that CO2 levels naturally move between 200ppm and 300ppm over hundreds of thousands of years. Which now leads me to another question: Have human beings exacerbated what was a naturally occurring rise in CO2 concentrations? If so, will the natural causes that reduced CO2 concentrations from 300ppm overcome that exacerbation?

acqq 12y ago
Your first link doesn't have any graph with 1750, your second, which is same as the third, also. The figure 1 in the pdf is specifically "Figure 1. U.S. Greenhouse Gas Emissions by Gas, 1990–2012" So I still don't see any graph since 1750. You probably wanted to paste something else? Humans have burned so much of C that CO2 concentration is alarmingly high, all the "natural" events during the last 400000 years simply didn't produce that much as fast as we do now, so we also can't expect anything to magically save us now. The oceans do get something that doesn't end in the air, but that's it. It happened before, it won't get better easy, that's what happened some 50 million years ago: http://en.wikipedia.org/wiki/Paleocene%E2%80%93Eocene_Thermal_Maximum http://en.wikipedia.org/wiki/Paleocene%E2%80%93Eocene_Therma... "Model simulations of peak carbon addition to the ocean–atmosphere system during the PETM give a probable range of 0.3–1.7 Pg C yr−1, which is much slower than the currently observed rate of carbon emissions.[60]" "Recovery: The δ13C record records a duration of around 120,000[22] to 170,000[1][61] years, slightly faster than the residence time of carbon in the modern atmosphere (100,000 to 200,000 years). A feedback system[62] would explain this slightly more rapid recovery time." There will be the way back, but in the scale of 100 thousand years. And now the increase happens much, much, faster than even that event 50 million years ago. Edit: maybe you mean this? http://cdiac.ornl.gov/trends/co2/graphics/lawdome.gif http://cdiac.ornl.gov/trends/co2/graphics/lawdome.gif ("Historical CO2 Records from the Law Dome DE08, DE08-2, and DSS Ice Cores") As you see, 1750 is not a relevant point at all (just as 1250 and 1500 aren't, it's just that the increments of 250 years are printed): the concentration values are something like 283 ppm around the year 1300, 286 around the year 1850. It's obvious that it really started (visibly more than what was around year 1300) with our higher use of coal in the 19th century (and oil in 20th). Before that it's effectively an oscillation (an order of a percent or two), after that it already reached the levels never seen during the last 600 thousand years - like 30% more since 1850 but also since at least 400000 years ago.

acqq 12y ago

Your first link doesn't have any graph with 1750, your second, which is same as the third, also. The figure 1 in the pdf is specifically "Figure 1. U.S. Greenhouse Gas Emissions by Gas, 1990–2012" So I still don't see any graph since 1750. You probably wanted to paste something else? Humans have burned so much of C that CO2 concentration is alarmingly high, all the "natural" events during the last 400000 years simply didn't produce that much as fast as we do now, so we also can't expect anything to magically save us now. The oceans do get something that doesn't end in the air, but that's it. It happened before, it won't get better easy, that's what happened some 50 million years ago: http://en.wikipedia.org/wiki/Paleocene%E2%80%93Eocene_Thermal_Maximum http://en.wikipedia.org/wiki/Paleocene%E2%80%93Eocene_Therma... "Model simulations of peak carbon addition to the ocean–atmosphere system during the PETM give a probable range of 0.3–1.7 Pg C yr−1, which is much slower than the currently observed rate of carbon emissions.[60]" "Recovery: The δ13C record records a duration of around 120,000[22] to 170,000[1][61] years, slightly faster than the residence time of carbon in the modern atmosphere (100,000 to 200,000 years). A feedback system[62] would explain this slightly more rapid recovery time." There will be the way back, but in the scale of 100 thousand years. And now the increase happens much, much, faster than even that event 50 million years ago. Edit: maybe you mean this? http://cdiac.ornl.gov/trends/co2/graphics/lawdome.gif http://cdiac.ornl.gov/trends/co2/graphics/lawdome.gif ("Historical CO2 Records from the Law Dome DE08, DE08-2, and DSS Ice Cores") As you see, 1750 is not a relevant point at all (just as 1250 and 1500 aren't, it's just that the increments of 250 years are printed): the concentration values are something like 283 ppm around the year 1300, 286 around the year 1850. It's obvious that it really started (visibly more than what was around year 1300) with our higher use of coal in the 19th century (and oil in 20th). Before that it's effectively an oscillation (an order of a percent or two), after that it already reached the levels never seen during the last 600 thousand years - like 30% more since 1850 but also since at least 400000 years ago.