https://www.democraticunderground.com/100210904287
I'm highlighting in the below just the parts that indicate humans are the cause of most of it. Part of the evidence is just the speed that it is occurring at -- e.g. warming is 10 times faster than when coming out of an ice age.
Climate Science: What You Need To Know, published December 2014
The below "transcript" is entirely my work listening to it on mostly a once-through basis. I indicate the APPROXIMATE time of each paragraph in mm:ss.
The informative part starts at 1:00
CO2 in the atmosphere has increased about 40% since 1790.
1:35:
Since 1970, when warming increase has been fastest, solar activity has been declining (graph shows solar activity increasing for about 5 years -- 1970-1975 -- and then declining to a little below its 1970 level.
1:45:
If the sun was to blame, it would heat the upper and lower atmospheres. Instead we see warming only in the lower layer -- the layer affected by the greenhouse gasses.
2:10:
studying trapped gasses in ice cores, CO2 levels are the highest in nearly a million years (the graph has "800,000 years ago on it" and ~190 ppm. It's about 410 ppm now)
2:20:
Earth is warming at about 10X the rate as at the end of an ice age.
2:35:
How do we know the increased CO2 levels is our fault? Answer: by looking at the isotope composition of CO2 in the atmosphere. Plants prefer aborbing CO2 with carbon 12 in it instead of carbon 13. So when plants are burned (by way of burning fossil fuels), the ratio of carbon 12 CO2 levels to carbon 13 CO2 levels increase -- and that's exactly what we see in the atmosphere.
2:58:
and it's not volcanic activity producing the CO2 -- volcanic activity produces only about 0.2 gigatons/year of CO2 -- about 1% of what humans do ( approximately 35 gigatons / year ).
3:10:
Other greenhouse gasses are increasing including methane from farm animals and natural gas processing, and nitrous oxide from fertilizer,
Climate models in the absence of increased greenhouse gas concentrations in the atmosphere predict cooling, and that is definitely NOT what's happening.
3:40: Each decade of the last 3 decades has been warmer than any other decade since we started measuring temperatures in the 1850s.
3:42: Since 1900 temperatures have increased almost a full degree (centigrade), and
most of that warming has occured since 1970.
3:50 Looking at tree rings and ice cores, the last 3 decades is probably the warmest in 8 centuries.
4:00: Oceans absorb about 90% of the heat added to the planet. Ocean temperatures are rising -- average sea level is rising at about 0.1" per year ... ocean levels on average have risen 8 inches since 1901 (due to water expanding as it warms, plus melting of ice that is on land).
4:30: about CO2 increased concentrations in ocean causing ocean acidification and affecting marine life with shells. We're on course to hit PH 7.8 in the oceans in 100 years -- which could wipe out 1/3 of ocean species.
4:45:
Levels of summer sea ice in the Arctic have decreased 40% since 1978 .. they might be at the lowest levels in 1400 years. That white ice surface reflects a lot of sunlight back into space. The dark sea water that is replacing it absorbs much more of the sun's energy (thus adding to global temperature -- a vicious cycle -- heat melts ice causing more dark ocean surface area absorbing more heat which melts more ice ... ).
5:00: With current CO2 increase trends, earth is on course to be 2.6 - 4.8 deg C warmer (4.7 - 8.6 deg F) in 100 years ... and oceans 1 meter higher.
5:20: The last time earth was only a few degrees colder, most of North America was covered in an ice sheet. So what will happen when temperatures are a few degrees warmer? We're going to have a bad time.
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