How do you rule out random climate variation scientifically? I'm curious, do we have enough data to say one way or the other?
I'm hesitant to post this, since it seems like detached scientific conversation about climate change has been in short supply. But perhaps.
One does not preclude the other. Was the climate different, often hotter and drier, in the past? Sure. Evidence shows that it was.
But does that mean that we aren’t leading ourselves in to a short/medium-term catastrophe by dumping enormous amounts of CO2 in to the environment now? No. The two are unrelated.
Imagine if we determined that the climate was on a natural cycle, such that the entire Earth would warm, fires and droughts would become commonplace, and that sea levels would rise as a result of global temperature. Would we just do nothing? I’d hope not. I’d hope that it would spur us in to action, to realise that our quality of life is about to radically change, that human migration will necessarily increase, that people living near the sea, or depending on water, will have their lives irrevocably changed.
That has happened in the past. We just didn’t have such a complicated society at the time, so the impacts were less. If you count the extinction of the Egyptian society as “less”.
It’s also happening now, except we are doing it. Voluntarily, with full knowledge of the ultimate result.
That seems, to people like me, a bit silly.
People always seem to talk as though it's one or the other, but it seems to me essentially impossible that it's not both.
Yes.
> and there is an underlying natural trend,
Yes.
> and that adds significant uncertainty to the magnitude and sign of those two factors?
Ooh you were so close to the trifecta.
This isn't disputable as randomness any more than an object can be said to have randomly fallen to the ground when dropped.
Here is one of countless sources you can find that explain this principle and the consequences: https://www.climate.gov/news-features/understanding-climate/...
Doesn't this mean that the correlation between CO2 levels and temperatures isn't that big?
1. Our current carbon levels haven’t been high long enough for their total effects in temperature to be felt yet, given the size of the system they must affect. 50 years is a blip on geological timescales.
2. There are cascading effects to high CO2 levels that will take longer to manifest themselves and which will raises the temperatures further. Permafrost melting and releasing methane is a possible example.
Ozone depletion measured CFCs in parts per trillion (US short scale).
You ask "do we have enough data". Well, the same data that gives us evidence of prior climate events is the same data that shows human emissions are climatologically significant. So if we have enough data to study random changes, we have enough to study the changes we are causing.
If you want to take a stance against man-made climate change, you'll actually need to do your own research first and have a really good reason why it's wrong. Can you yourself list all the data sources that go into climatology and why they aren't adequate?
I had a longer comment prepared, but as you say, responding to accusations tends to get boring.
If you want to have a conversation about this, though, it would be nice.
[1] https://www.ipcc.ch/srocc/chapter/summary-for-policymakers/
https://www.bloomberg.com/graphics/2015-whats-warming-the-wo...
To me, it seems like (strong) evidence that climate can change.
And that there is a cause of this change, and that the cause that can be found. Maybe volcanic, meteoric, related to vegetation levels, or other?
Which is, I think, the _opposite_ of random. It is understandable and predictable.
> How do you rule out random climate variation scientifically?
Outside of quantum physics, "it was random" is not a scientific explanation. Science finds causes.
When applied to "our current climate change", the idea that climate can change and change a lot, in response to causes, well, that provides the opposite conclusion to yours doesn't it: we can see the causes this time.
Negative. It's quite possible (even likely) that the odds of a major hurricane hitting Florida next week are down to "a non-linear, dynamic system" and you're tying to predict which why the storm will "veer off wildly", while the average number and total intensity of storms over the next ten years is neither of those.
That allows us to reduce your question to how do we rule out that the increases in greenhouse gases are due to random variation?
For CO2, we can answer that by looking at different carbon isotopes. CO2 in living plants, CO2 in long dead plants, CO2 in volcanic gas emissions, and CO2 from weathering rock all have distinctly different ratios of carbon isotopes. By looking at the isotope distribution on the carbon in the atmosphere, we can show that most of the increase is from long dead plants--in other words, from burning coal and oil.
I am interested in the scientific methodology that rules out such variations and confirms that fossil fuels are in fact responsible.
The time period is an obvious one: we seem to be seeing spikes in one century vs millennia. But the details of those spikes matter in comparison to our total historical record; hence the curiosity.