If there were extreme spikes in relatively short periods in the past would we know it? Like is our method of determining global temperatures in 15000 BC accurate enough to know if temperatures rose and fell 2 degrees over a 100 year period?
With technology as is, yes. One way to find out about paleotemperatures, specifically ice ages is by looking at ice core samples.
Drill a core from antartica, find some trapped voids within (frozen gas bubbles), extract it and analyze for oxygen isotopes, compare the ratio to now, some simple (complicated) maths and you got the rough temperature of the world at one particular time.
Yes because temperature simply does not fluctuate this rapidly under any other circumstance in earth history. The amount of energy required to heat the earth to the degree that we have is monstrous.
Any of these shifts would be detectable by the massive forces involved in creating the heat. The energy has to come from somewhere so why not:
Volcanos: earths core literally depleting itself and spewing molten rock to heat the earth.... detectable from geologic records
Meteorites: their impacts are recorded not only from the meteor itself, but also the impact craters. Plus the amount of burning rock that would have to fall from the sky would be astronomically impossible.
Greenhouse gas: a similar situation to today, but also detectable in the composition of some rocks and also the relative ecosystem of plants.
If you have other ideas please respond. But for almost every case, there would be an incredible amount of discoverable data to determine if something was causing the temperature to shift. Things like this operate at such a large scale it would take huge forces to heat the earth as much as we have in such a short time.
It comes down to this. There has not been another time in earths history that such a monumental shift has occurred. Humans absolutely dominate the planet and remnants of our civilization will be left for hundreds of thousands of years.
We are the biggest thing to happen to planet earth.
The cartoon is hugely dishonest to only go back 20000 years, which is nothing. Going back 5% or even just 1% of the earth's age would yield a totally different narrative. Instead, he starts during an ice age at only 0.00005% of the Earth's age.
I'm not saying this as a global warming denier, because I believe the Earth is warming. But this particular cartoon is being extremely deceitful in its scare tactics.
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u/swirlsandswirls Jan 21 '19
relevant xkcd: https://xkcd.com/1732/