"This isn't a binary contest where one theory must replace the other. "

There can only be one dominant theory.

BTW, can't help but notice that you haven't offered the slightest evidence for your myriad assertions.

"Thanks for the copy-and-paste, mhaze."

Well I used quotes where appropriate.

Climate attribution isn't a Highlander episode, mhaze.

//There can only be one dominant theory.//

Multiple forcings operate simultaneously. Solar variability, volcanic aerosols, internal variability and greenhouse gases all contribute. The question is which forcings explain the magnitude and timing of the recent trend.

//BTW, can't help but notice that you haven't offered the slightest evidence for your myriad assertions.//

1. Solar activity has not shown a sustained upward trend since the 1970s.

See IPCC AR6 WG1, Chapter 2 (solar forcing section). Satellite measurements of total solar irradiance since 1978 show cyclical variation but no long-term upward trend:
http://www.ipcc.ch/report/ar6/wg1/chapter/chapter-2

NASA – Solar Irradiance Data (TSI Composite Records):
http://lasp.colorado.edu/lisird/data

2. Cosmic ray flux has not shown a sustained downward trend over that same period.

Neutron monitor records (e.g. Climax, Oulu datasets) show the 11-year cycle clearly:
http://cosmicrays.oulu.fi

See Usoskin et al. (2017) for cosmic ray reconstructions and instrumental-era trends:
http://link.springer.com/article/10.1007/s41116-017-0006-9

3. Climate model runs using only natural forcings (solar + volcanic) do not reproduce the late-20th-century warming trend.

Hegerl et al. (2007), IPCC AR5 Chapter 10, and IPCC AR6 WG1 Chapter 3 present detection-and-attribution analyses showing that simulations including only natural forcings (solar + volcanic) fail to reproduce observed post-1970 warming, whereas including greenhouse gases does.
http://archive.ipcc.ch/publications_and_data/ar4/wg1/en/faq-9-2.html

Additional support from IPCC AR5 detection & attribution chapter:
http://www.ipcc.ch/site/assets/uploads/2018/02/WG1AR5_Chapter10_FINAL.pdf

Those are not rhetorical claims. They're published attribution findings.

So, where's the evidence for your claims?

http://i.giphy.com/1Zbeweu52ZaQE.webp

"When scientists test this properly, they don't just eyeball graphs. They run simulations with different drivers switched on and off. If you exclude greenhouse gases, the late-century warming largely disappears in those simulations. Put them back in, and the models produce the upward trend we actually observed."

Just another, YET another, one of assertions JD makes that he hopes to never have to provide evidence for. As as expect, he hasn't.

You need to show us where this has happened. More importantly, you need to show that the simulations have been correctly calibrated by showing that they are able to recreate past temperature changes and correctly predict future changes.

mhaze,

You've now said twice that I "haven't provided evidence." That's simply not accurate.

I linked sources that explicitly show the "natural forcings only" vs "natural + anthropogenic" comparison you asked for:

- IPCC AR4 FAQ 9.2: http://archive.ipcc.ch/publications_and_data/ar4/wg1/en/faq-9-2.html
- IPCC AR5 WG1 Chapter 10 (Detection & Attribution): http://www.ipcc.ch/site/assets/uploads/2018/02/WG1AR5_Chapter10_FINAL.pdf

Both assess the same basic point: simulations using only natural forcings (solar + volcanic) do not reproduce the late-20th-century warming trend, including anthropogenic forcing does.

If you dispute that finding, say so and explain why. But repeating "no evidence" after citations have been provided isn't engagement.

You also shifted the standard to "show they're correctly calibrated" and "predict future changes." Hindcasting historical temperature evolution using known forcings is exactly what detection-and-attribution work tests, and that's what those chapters are assessing.

If you reject this category of evidence (assessment of the attribution literature), then spell out what category you would accept. Otherwise we're not talking about the same thing.

Still waiting on your evidence too, by the way. I take it we're not going to get it.

"You also shifted the standard to "show they're correctly calibrated" and "predict future changes." "

No. That was part of my original point. I guess you (ahem...) conveniently missed that. There's not much point in relying on this or that model to forecast the future if it can't hindcast the past.

"Still waiting on your evidence too"

Well go back and read all the stuff I posted and the links regards Svensmark. I guess you (ahem...) conveniently missed that.

Whether it was original or added later isn't the issue, mhaze.

//That was part of my original point.//

The issue is whether attribution studies test hindcasting. They do. That's exactly what the chapters I linked assess.

//There's not much point relying on this or that model to forecast the future if it can't hindcast the past.//

Agreed in principle.

That's why detection-and-attribution work compares model runs using historical forcings against observed 20th-century temperature evolution. The sources I linked show that simulations using only natural forcings do not reproduce the late-20th-century warming trend, whereas including anthropogenic forcing does.

//Well go back and read all the stuff I posted and the links regards Svensmark.//

I've read them.

They describe a mechanism. They do not demonstrate that natural forcings alone reproduce the observed late-20th-century warming. That's the specific claim under discussion.

I guess you (ahem...) conveniently missed that.