On Thursday, August 9, 2018 at 3:22:57 AM UTC-6, Martin Brown wrote:

On Tuesday, August 7, 2018 at 7:40:03 AM UTC-6, Quadibloc wrote:
The tipping point is in sight:

https://www.cbc.ca/news/technology/w...port-1.4775649

They are probably being overly pessimistic. However, I think the
incidence of wildfires in the USA and persistent drought in Australia
may yet force the climate change deniers to change their tune.

Some deny global temperature increase, but others admit it is happening
but deny CO2 et al are responsible. MODTRAN supports the latter.

It is a shame that Texas cannot be laid waste by climate change induced
catastrophes. California has been trying quite hard - they don't deserve
to bear the brunt of natures fight against the fossil fuel lobby.

That's a very biased paragraph.

http://climatemodels.uchicago.edu/modtran/

T_offset = 0, T_ground = 298.52 K, Upward heat flux = 298.52 W/m²

T_offset = 2, T_ground = 301.7 K, Upward heat flux = 307.44 W/m²

Conditions are CO2 = 400 ppm, Tropical region, No clouds

Clouds hold the heat in, but reflect more solar energy.

The model also shows that DOUBLING the CO2 concentration to 800 ppm
has a minimal effect on outgoing heat:

T_offset = 0, T_ground = 299.7 K, CO2 = 800 pp,,
Upward heat flux = 295.2 W/m²

To get the UHF back to 298.5 W/m², increase T_offset to 0.75 K..
So doubling the CO2 level increases the ground temperature by 2 K.
That doesn't look like a "tipping point."

If you believe these figures are accurate to 5 sig fig then you are no
scientist.

If you believe the IPCC results are accurate to 5 sig fig then YOU are
no scientist :-)

Don'tcha just love oversimplification for effect?
Is Big Carbon's pocket money allowance taxable?

Using simplified models for a sanity check on "more complex" one is a
valid scientific operation.

Using a model that completely ignores the thawing of permafrost and
clathrates leading to bulk methane escaping in the Siberian wilderness
will obviously not show any kind of tipping point. There is serious
hysteresis in the climate system once you go past a certain point and
the permanent ice caps and glaciers are forced into retreat.

I tormented one of the much earlier models trying to boil the oceans at
the equator by making a big step change in CO2. Even at 3K per doubling
of CO2 it would require an increase of about 2^14 to get the worst case
temperatures that high - about 6 bar of CO2 (making it impossible for
life to survive outdoors in some places is much easier 8x will do that).

Things get quite nonlinear as the equatorial seas approach boiling point
so this was pushing the model well outside reasonable bounds.

--
Regards,
Martin Brown

We're probably not concerned about what happens when the oceans boil :-)