Global warming in 2100

[Tom Mazanec]

What do you think the Earth's warming over pre-industrial level will be at the end of the century?

[Noclevername]

If we're still a functional civilization by then it'll be because we managed to get away from burning fossil fuels, slashing forests, plasticizing the oceans, and reproducing like bacteria. We'll still be dealing with the aftermath of our present day damage, but if we have too much increase in temp we will reduce our population drastically and involuntarily. In which case our industrial capacity will also be greatly reduced. One way or another, there will be a correction. I hope it's one of our choosing.

[Tom Mazanec]

I'm a pessimist, given human nature and Realpolitik. If we survive as a civilization, it will be at Herculean effort.

[profloater]

If we use 0.2 C per decade that’s heading for the 2 degree point often talked about. I am pessimistic in that i think we will hit 2 C before 2100 but optimistic that we will survive the worsening extreme weather although there will be areas that become uninhabitable. I have no idea if 2 is the feared tipping point that models predict will be irreversible in the short term of centuries.
As a technologist I am optimistic that as we take it more seriously we will find ways to both adapt and ameliorate the warming. To go further into futurology would involve political discussion.

[Tom Mazanec]

I understand we are already at 1.5, and don't forget the feedbacks.

[profloater]

Or maybe less?
https://climate.nasa.gov/vital-signs...l-temperature/

[Spacedude]

Last I heard was that the arctic icecap will be gone by the summer of 2030 or thereabouts. One thing I've noticed about ice is that when it's all melted my drink warms up at an accelerated rate.

[Tom Mazanec]

Or maybe less?
https://climate.nasa.gov/vital-signs...l-temperature/

From the link:
This graph illustrates the change in global surface temperature relative to 1951-1980 average temperatures.

1951-1980 is not pre-industrial.

[profloater]

From the link:
This graph illustrates the change in global surface temperature relative to 1951-1980 average temperatures.

1951-1980 is not pre-industrial.

Ok i am happy to start from any date you think is the baseline, but it should be specified because it was never a constant. Early dates of course are derived from ice cores and similar proxy systems and in fact the ocean and air values we have now are recent technology so if you want to poll on 2100 value, let’s start somewhere on the graph.

[Tom Mazanec]

OK then, 1800.
I understand tree clearing in the 19th Century was actually more important than 19th Century coal burning, so that is a good year to start.

[Squink]

With or without methane clathrate catastrophe?
That adds about 4°C to my guess.
I'm assuming no such nasty tipping point, but put the odds of one near 50%.

[Tom Mazanec]

Personally, I expect a methane catastrophe of some magnitude.
Choose which you want to guess.

[profloater]

Personally i am worried about the gulf stream weakening, (there is a separate thread), it could be a negative feedback on the arctic warming ( the gulf stream sends warm water into the arctic region) but it might mean much more severe winters in Europe. Too soon to know but we will not have to wait till 2100 to find out! Maybe it will recover.

[nota]

depends a bit on the sun spot cycle and total energy input
vs what happens on earth with CO2 rates and if the methane clathrate is released

we do not have a good understanding of the sun cycles
are we in a short dip or a decline into a minimum over a longer time
all stars are variable but we have limited understanding of how variable our star is

my guess is if the sun is going to a minimum less then 2c more if no methane clathrate addition
if a normal sun returns 4c
and if the sun goes into a peak cycle period maybe more

I am somewhat surprised in the lack of solar input discussion in this thread and GW in general

that is independent of CO2 rates

I do think the lack of cooling in the face of a solar input slight drop
is real time proof of CO2 effect on heat retention

[Tom Mazanec]

nota
Solar variability is at least an order of magnitude less than the influence of Greenhouse Gasses.

[Swift]

nota
Solar variability is at least an order of magnitude less than the influence of Greenhouse Gasses.

From the American Institute of Physics

(my bold)

Since it is the Sun's energy that drives the weather system, scientists naturally wondered whether they might connect climate changes with solar variations. Yet the Sun seemed to be stable over the timescale of human civilization. Attempts to discover cyclic variations in weather and connect them with the 11-year sunspot cycle, or other possible solar cycles ranging up to a few centuries long, gave results that were ambiguous at best. These attempts got a well-deserved bad reputation. Jack Eddy overcame this with a 1976 study that demonstrated that irregular variations in solar surface activity, a few centuries long, were connected with major climate shifts. The mechanism was uncertain, but plausible candidates emerged. The next crucial question was whether a rise in the Sun's activity could explain the global warming seen in the 20th century? By the 1990s, there was a tentative answer: minor solar variations could indeed have been partly responsible for some past fluctuations... but future warming from the rise in greenhouse gases was far outweigh any solar effects.

[Copernicus]

It is hard to tell what the global warming will be. With all the doom and gloom, the world population will be lucky to be at 25 million by then. Trailing CO2 would probably raise the temp by 2 degrees C by that time.

[Swift]

From the Climate Lab Book (a blog written by climate scientists), a comparison and a discussion of the various projections.

This page is an ongoing effort to compare observations of global temperature with CMIP5 simulations assessed by the IPCC 5th Assessment Report. The first two figures below are updated versions of Figure 11.25a,b from IPCC AR5 which were originally produced in mid-2013.

The first panel shows the raw ‘spaghetti’ projections, with different observational datasets in black and the different emission scenarios (RCPs) shown in colours. The simulation data uses spatially complete coverage of surface air temperature.

The second panel shows the AR5 assessment for global temperatures in the 2016-2035 period. The HadCRUT4.6 observations are shown in black with their 5-95% uncertainty. Several other observational datasets are shown in blue. The light grey shading shows the CMIP5 5-95% range for historical (pre-2005) & all future forcing pathways (RCPs, post-2005); the grey lines show the min-max range. The dark grey shading shows the projections using a 2006-2012 reference period. The red hatching shows the IPCC AR5 indicative likely (>66%) range for the 2016-2035 period.

These projections are generally out to "only" 2050, as I suspect the uncertainty in projecting out to 2100 becomes unreasonable (my understanding is that a lot of the uncertainty is in "what will humans do" and much less in details of various climate models).

[nota]

nota
Solar variability is at least an order of magnitude less than the influence of Greenhouse Gasses.

but it is a very complex system
with lots of factors
as this is an astronomy board
and we do not really have a good understanding of our star cycles

or upper or lower limits that our star can show

a better idea of the range of future fluctuation is needed
as is better prediction of cycle output

for CO2 we need to understand why the effects lag in the records
making it look that the heat causes the high CO2 numbers later
a very odd reverse effect to the results [ ice cores mostly]

[profloater]

The last million years show more ice ages than interglacials and orbital variations seem to be the driver but impacts and volcanism are also important, IMO, as are the plate tectonics which change the ocean currents, so an impact now would change everything. You would expect every interglacial to warm progressively due to more water in the atmosphere yet there have been cycles. The recent rate due to CO2 upsetting a balanced system is accepted as manmade and might add positive feedback in releasing trapped methane or modified cloud cover like this summer (northern hemisphere) widespread heatwaves. Projecting to 2100 in an accelerated technology world is like asking someone in, say 1800, Tom’s chosen date , to speculate on airtravel and nuclear energy. We live in changing times.

[Copernicus]

One could make an argument that higher CO2 levels buffer the affects of orbital variations.

[Swift]

One could make an argument that higher CO2 levels buffer the affects of orbital variations.

Really? Could you explain that argument? I suppose orbital variations that lead to cooler temperatures would be countered by higher CO2 levels, but variations that lead to warmer temperatures would be that much worse. I don't see how this is buffering?

[profloater]

I suppose co2 might delay or avoid the next ice age, but the rate of T rise in the last 20 years suggests a different timescale for our problems. We are now able to measure deep ocean T and soon the complete wind picture ( I refer to the recent pilot wind survey satellite) so climate changes will be better mapped than ever before. We need to start thinking about regional changes rather than just a global figure, . Did you see the recent excessive monsoon in India for example?

[Copernicus]

Really? Could you explain that argument? I suppose orbital variations that lead to cooler temperatures would be countered by higher CO2 levels, but variations that lead to warmer temperatures would be that much worse. I don't see how this is buffering?

I just say that because the temperature swings have been more wild the last million years, when the CO2 levels were lower. The following is a chart of global temperature swings the last 2 million years. https://www.google.com/search?q=temp...-PcQrek6gn3DM:

The following graph shows CO2 levels over a long period of time with millions of years at about 500 ppm.

https://www.google.com/search?q=carb...VOrvL2EIEh-IM:

[Copernicus]

Really? Could you explain that argument? I suppose orbital variations that lead to cooler temperatures would be countered by higher CO2 levels, but variations that lead to warmer temperatures would be that much worse. I don't see how this is buffering?

This person's argument, that without enough CO2 the greenhouse affect would go away and it would be an icebound earth. https://phys.org/news/2010-10-carbon...mperature.html

[Swift]

I just say that because the temperature swings have been more wild the last million years, when the CO2 levels were lower. The following is a chart of global temperature swings the last 2 million years. https://www.google.com/search?q=temp...-PcQrek6gn3DM:

The following graph shows CO2 levels over a long period of time with millions of years at about 500 ppm.

https://www.google.com/search?q=carb...VOrvL2EIEh-IM:

The first graph shows temperature fluctuations over the 2 million years and does not show CO2 levels, so I don't know how you find a correlation.

The second graph only shows CO2 levels, not temperature fluctuations.

I still think claiming a cause-effect relationship between CO2 levels and buffering of temperature fluctuations is a big reach. I can't imagine what mechanism would cause such a thing. And I don't know what any of this has to do with "snowball Earth". Of course not enough CO2 is bad; that is not remotely our problem now. And that story ends with this:

"The Intergovernmental Panel on Climate Change has fully documented the fact that industrial activity is responsible for the rapidly increasing levels of atmospheric carbon dioxide and other greenhouse gases. It is not surprising then that global warming can be linked directly to the observed increase in atmospheric carbon dioxide and to human industrial activity in general."

So if you are somehow trying to argue against AGW, then the very story you linked to argues the opposite.

[Copernicus]

The first graph shows temperature fluctuations over the 2 million years and does not show CO2 levels, so I don't know how you find a correlation.

The second graph only shows CO2 levels, not temperature fluctuations.

I still think claiming a cause-effect relationship between CO2 levels and buffering of temperature fluctuations is a big reach. I can't imagine what mechanism would cause such a thing. And I don't know what any of this has to do with "snowball Earth". Of course not enough CO2 is bad; that is not remotely our problem now. And that story ends with this:


So if you are somehow trying to argue against AGW, then the very story you linked to argues the opposite.

No, no argument with human caused global warming/cooling/climate change, due to human activity.

[Robert Tulip]

I think we will keep temperature rise below 1.5 degrees by developing new technology to remove a trillion tonnes of carbon from the air and sea, combined with solar radiation management, recognising global warming as the main security agenda for our planet.

[Roger E. Moore]

Global warming good news: The Arctic Ocean is open for business!

https://www.forbes.com/sites/niallmc.../#5a5cda906c2b

Container ships can get through fairly well and more often, sail completely around Eurasia.

[Swift]

Global warming good news: The Arctic Ocean is open for business!

https://www.forbes.com/sites/niallmc.../#5a5cda906c2b

Container ships can get through fairly well and more often, sail completely around Eurasia.

Compared to the destruction of countless species and the disastrous impacts on humans, I hardly find anything to be happy about.