Which part of the post I linked was rhetoric? Here it is again
It's entirely caused by human activity. Ancient climatic fluctuations are caused by changes in solar Flux entering the atmosphere and volcanic and erosional activity. All these are well known and well accounted for and these would be causing the
climate to cool right now. Instead, due to CO2 generation, it's warming.
https://earthobservatory.nasa.gov/Features/GlobalWarming/page4.php
Firstly, the hypothetical natural cycle would have to explain
the observed "fingerprints" of greenhouse gas-induced warming. Even if, for the sake of argument, we were to discount the
direct measurements showing an increasedgreenhouse effect, other lines of evidence point to anthropogenic causes. For example, the troposphere (the lowest part of the atmosphere) is warming,
but the levels above, from the stratosphere up, are cooling, as less radiation is escaping out to space. This rules out cycles related to the Sun, as solar influences would warm the entire atmosphere in a uniform fashion. The only explanation that makes sense is greenhouse gases.
What about an internal cycle, perhaps from
volcanoes or the
ocean, that releases massive amounts of greenhouse gases? This wouldn't make sense either, not only because scientists keep track of volcanic and oceanic emissions of CO2 and know that they are small compared to anthropogenic emissions, but also because CO2 from fossil fuels has its own fingerprints. Its isotopic signature is depleted in the carbon-13 isotope, which explains why the atmospheric ratio of carbon-12 to carbon-13 has been going up as anthropogenic carbon dioxide goes up. Additionally, atmospheric oxygen (O2) is decreasing at the same rate that CO2 is increasing, because oxygen is consumed when fossil fuels combust.
A natural cycle that fits all these fingerprints is nearly unfathomable. However, that's not all the cycle would have to explain. It would also have to tell us whyanthropogenic greenhouse gases are
not having an effect. Either a century of basic physics and chemistry studying the radiative properties of greenhouse gases would have to be proven wrong, or the natural cycle would have to be unbelievably complex to prevent such dramatic anthropogenic emissions from warming the planet.
The human fingerprint in global warming
The first four pieces of evidence show that humans are raising CO2 levels:
- Humans are currently emitting around 30 billion tonnes of CO2 into the atmosphere.
- Oxygen levels are falling as if carbon is being burned to create carbon dioxide.
- Fossil carbon is building up in the atmosphere. (We know this because the two types of carbon have different chemical properties.)
- Corals show that fossil carbon has recently risen sharply.
Another two observations show that CO2 is trapping more heat:
- Satellites measure less heat escaping to space at the precise wavelengths which CO2 absorbs.
- Surface measurements find this heat is returning to Earth to warm the surface.
The last four indicators show that the observed pattern of warming is consistent with what is predicted to occur during greenhouse warming:
- An increased greenhouse effect would make nights warm faster than days, and this is what has been observed.
- If the warming is due to solar activity, then the upper atmosphere (the stratosphere) should warm along with the rest of the atmosphere. But if the warming is due to the greenhouse effect, the stratosphere should cool because of the heat being trapped in the lower atmosphere (the troposphere). Satellite measurements show that the stratosphere is cooling.
- This combination of a warming troposphere and cooling stratosphereshould cause the tropopause, which separates them, to rise. This has also been observed.
- It was predicted that the ionosphere would shrink, and it is indeed shrinking.
