[EvaH (OP)]

Alex says:

There is a lot of talk about global warming and how catastrophic it will be. I have heard a major problem is the earth's poles are heating up too rapidly, and if this heating up could be delayed a month or so it would solve a lot of problems. If this is the case then to my mind the solution is simple - put an umbrella in space over the pole and move it from pole to pole each weather cycle using ionic positioning rockets. The amount of heat from the sun could be controlled by standing the umbrella on end allowing more heat from the sun as required. As this technology develops it could also be used to control hurricanes and typhoons by heating or cooling areas around them allowing them to disapte safely at sea.

What do you think?

[Petrochemicals]

There has been alot of investigation into this sort of technology,

https://en.m.wikipedia.org/wiki/Space_sunshade

Personally I think that this sort of technology is very dangerous, being as we do not seem to understand the environment well at present, if we where to remove too much energy from the system we could end up pushing the climate too far the other way, causing a global cooling and famine, as is seen after volcanic eruptions.

[alancalverd]

Not much point in shielding the poles since they only receive sunlight (and not a lot of it) for half the year, and snow and ice are very reflective anyway. The problem is the chaotic cyclic water content of the atmosphere, which determines atmospheric temperature, weather and climate, and is not controllable.

It would be great to limit the heat input to hurricane cells.  You need a 500 km diameter umbrella in a pseudostationary orbit, that can be moved to track a 30 mph system on the surface - a just-feasible idea.  The umbrella needn't be a continuous sheet: 50% holes would be enough to prevent a cyclone developing into a hurricane. The trick would be to spot the naughty ones, because killing all the cyclones would seriously disrupt everyone's climate!

[MarkPawelek]

The propaganda has been going on since the 1980s. The idea of catastrophic climate change derives from positive feedback term(s) in climate models. But there are no positive feedback terms in the real climate system. We should not take models seriously unless they've been tested and validated to the same, or similar, level as scientific ideas such as hypotheses and theories are.

[evan_au]

there are no positive feedback terms in the real climate system

One positive feedback factor is the polar ice sheets
- These regions are warming quickly, due to climate change, as shown by temperature records
- The ice cover is reducing, year by year, as shown by satellite images
- Reduced ice cover means that the exposed sea or land absorbs more sunlight in the summer months (instead of reflecting it away into space from the snow/ice)
- This means that the air temperature warms over polar regions
- Warmer air means faster melting
- Faster melting means more exposed land/sea
...and you can see where this is going!

There are some slight compensations - slightly warmer sea means more humidity, which can lead to higher snowfall (more reflective) - but it can also lead to rain, which washes away whatever snow is left (less reflective).
- But overall, "positive feedback" is exactly what it is!

See: https://en.wikipedia.org/wiki/Climate_change_feedback

[Petrochemicals]

There are some slight compensations - slightly warmer sea means more humidity, which can lead to higher snowfall (more reflective) - but it can also lead to rain, which washes away whatever snow is left (less reflective).
- But overall, "positive feedback" is exactly what it is!

See: https://en.wikipedia.org/wiki/Climate_change_feedback

Aside from the more global and general positive feedback of  less solar radiation being reflected , lying snow at a local level  stops the earth at the surface absorbing radiation in a short term period. This means that further snow falls onto cold ground so it settles, this further means the local environment is below freezing, thus meaning a feedback loop in a local level, over a large enough area this can affect weather systems like the rainforests. This will in turn lead to the global feedback of atmospheric temperatures as snow pack rises/falls.

http://digitaljournal.com/tech-and-science/science/the-amazon-s-weather-engine-has-impacts-on-rainfall-globally/article/556718

[alancalverd]

But there are no positive feedback terms in the real climate system.

The most important positive feedback is water. The vapor has an enormous infrared absorption spectrum, the latent heat of melting and vaporisation is huge, it exists and moves between all three phases in the atmosphere, it is highly reflective in solid form, the solid anomalously floats on the liquid and thus controls heat exchange between the liquid and the atmosphere, it covers 70% of the earth's surface as liquid or solid and is present in evaporable form in every part of the solid surface.

The problem is that the water cycle, though bounded by ice ages, is inherently  chaotic and we have no means of measuring its atmospheric distribution in real time to a useful precision. So the IPCC ignores it.

It happens that atmospheric carbon dioxide is a lot easier to measure and historically tracks the water content as found in ice cores. The big mistake in climate modelling is to  assume that CO2 is the driver of climate, but as the historic data shows the CO2 graph lagging several years behind the H2O curve, it is quite clear than H2O is the thermostat and positive feedback element,  and CO2 is merely a convenient thermometer.

[vhfpmr]

I think methane released from melting permafrost is another positive feedback, isn't it?

[Bored chemist]

we have no means of measuring its atmospheric distribution in real time to a useful precision.

Yes we have.
It's essentially similar in many ways to measuring CO2.

So the IPCC ignores it.

Well... they don't really.
But the reason it doesn't feature heavily in models of anthropogenic global warming is that the amount of water in the air is often governed essentially by the temperature. (Near 20C the change in vapour pressure is close to 12% per degree).
Whereas the concentration of CO2 is strongly dependent on human activity.
We are responsible for a roughly 1 in 3 change in the CO2 concentration.
But we couldn't add much more water to the air if we tried- it would fall out again.

When you are looking at a change in a system, you don't usually focus on the thing that does not change.

[evan_au]

The most important positive feedback is water. The vapor has an enormous infrared absorption spectrum, the latent heat of melting and vaporisation is huge...

This is why it is absolutely essential that water be modeled in computer simulations of the weather and the climate.
And it is.
All the computer models include the effects of water in all 3 states, and model the movement between all states, horizontally, vertically and temporally.
That is how the weather forecast is able to forecast rainfall.

Since these computer models are the basis for IPCC projections, you can rest assured that IPCC does take the details of water into account in their projections.

The problem is that the water cycle... is inherently  chaotic and we have no means of measuring its atmospheric distribution in real time to a useful precision.

Chaos is inherent in all fluid dynamics problems, including the weather (even without the water content).
- That's why such big computer systems are needed for weather and climate forecasting.

Starting around the mid-1800s, a nationwide network of weather stations has been developed. As well as wind speed, they also measure humidity and rainfall (ie water).
- More recently, most countries have airport weather radar, which measures rainfall over a large area around major cities.
- Even more recently, satellites have been providing continuous coverage of cloud, water vapor content and snow cover

That provides the calibration feedback into the weather models so that they always have a precise distribution of water in the atmosphere.

See: https://en.wikipedia.org/wiki/Weather_station
https://earth.esa.int/web/guest/missions/esa-operational-eo-missions/envisat/instruments/sciamachy-handbook/wiki/-/wiki/SCIAMACHY%20Handbook/Water+Vapour++H2O

[alancalverd]

But the reason it doesn't feature heavily in models of anthropogenic global warming is that the amount of water in the air is often governed essentially by the temperature.

I think you have just given an example of positive feedback, which is what Reply #3 was about .

You seem to have fallen into the same trap as the IPCC. Climate is inherently unstable and has always changed. I don't see the word "anthropogenic" in the IPCC's title or mandate. From the IPCC website:

The Intergovernmental Panel on Climate Change (IPCC) was established in 1988 to provide policymakers with regular scientific assessments on the current state of knowledge about climate change.

There would be little mileage in simply reporting the data and admitting "it's inherently chaotic and driven by something we can't measure, predict or control". Thousands of careers would grind to a halt and  good friends of mine would not be able to excuse polluting Antarctica with their presence in the name of "research". So most of the focus  is on mining the rich seam of human vanity, guilt and easy measurement that is anthropogenic carbon dioxide.

Every time I'm invited to speak on the merits of vegetarianism as a means to prevent climate change, I explain how farm animals account for 25% of anthropogenic CO2, then point out that abandoning meat  won't make a ha'porth of difference to the climate, but nobody listens to the second half because the public wants to believe that anthropogenic CO2 is the driver. Why should I complain? If they thought otherwise, I'd lose my audience!

[alancalverd]

This is why it is absolutely essential that water be modeled in computer simulations of the weather and the climate.

BC is usually the first to point out that weather is not climate. It must be past his bedtime!

I have yet to see a computer simulation or even a credible analytic statement that explains why the Vostok ice core  temperature graph leads the CO2 curve by about 500 years, or why the Mauna Loa data shows temperature leading CO2 thoughout the year.

[evan_au]

(the climate) is inherently chaotic and driven by something we can't measure, predict or control

Yes, climate (and weather) is inherently chaotic.
- That's why weather modelers are one of the first (non-classified) customers for high-powered computer systems. 
- To double the resolution of your model, you need 16 times more compute power and memory and disk storage. Double the resolution in latitude and longitude, and double the resolution vertically, and halve the time step = 16 times the compute power to run the model
- That's why the computers run a model multiple times, with different random variation to account for the measurement uncertainties, to get an "average" prediction (and a measure of the variability around the average)
- That's why teams in different countries run their own models on their own computers, so that they can correct each other, and a software error in one model does not affect the IPCC consensus.

But, climate (and weather) is driven by things we can measure:
- Distribution of oceans and land masses
- Daily day/night cycle
- Annual seasonal cycle
- Atmospheric & ocean temperatures & pressures
- Atmospheric composition: Includes water, CO₂, methane, etc

The best weather forecasting models today regularly give a decent 7-day prediction (and a 10-day indication)
- This is good validation of their computers and the models they are using
- Researchers are pushing towards a 14-day prediction,
- but this requires even more detailed models on their latest big computers
- and tying in even greater volumes of data in real time from more sources (including new types of satellite sensors)

CO₂ and methane are increasing due to human activities. They break down and are recycled at known rates (for CO₂ this is something like a century).
- Human-generated greenhouse gases are something that humanity is able to control. Just like the Montreal protocol controlled fluorocarbons - only harder, because the economy currently depends more on energy and meat than on fluorocarbons.
- So the climate modelers always take the current trend, a low estimate and a high estimate for human-generated greenhouse gases
- As I understand it, the actual climate has always been closer to the "high" estimates

weather is not climate

This is true. But they both obey the Navier-Stokes equations.
- That means they can run essentially the same code on identical computers.
- The difference is the timescale:
        - Personally, I suggest that the Climate is an average over at least 11 years, just in case, someday, they manage to find a tangible link between the 11-year sunspot cycle and Earth's climate.
       - Weather is bound by the chaos in the system to just a week or two (maybe we will do better with a quantum computer, some day?)

a) The Pacific ocean El Niño/La Niña (and similar patterns in the Indian ocean) get an indication perhaps 6 months in advance
b) We have understood the annual seasonal patterns for millennia
- Apart from (a) and (b), there is a very clear distinction between Weather (<2 weeks) and Climate (≥11 years)

To account for these different timescales, the main difference between Weather and Climate is what you consider "constant" and "variable" in your computer model:
- For a Weather forecast (< 2 weeks), they assume the CO₂ concentration is a constant (it is changing too slowly to make a difference)
- For a Climate forecast (≥ 11 years), they assume the CO₂ concentration is changing year-by-year (with high, medium & low estimates)
- For a Climate forecast (≥ 11 years), they assume the distribution of and masses is constant (they are changing too slowly to make a difference)

[Bored chemist]

I think you have just given an example of positive feedback, which is what Reply #3 was about .

Only MarkPawelek is naive enough to think that there's no positive feedback.
There are at least 3 major pathways for it
1 Ice is reflective
2 Methane trapped as hydrates would be a very potent greenhouse gas
3 water vapour

I'm sure I have seen you failing to properly understand the idea of a saturated transition as you seek to explain why CO2 isn't important to climate change.
Well, that argument is much more nearly valid for water vapour.
So the change in net solar gain with water vapour in the air is smaller.

Interestingly, CO2 isn't- in itself- a positive feedback  mechanism. More CO2 leads to warming, but it directly doesn't lead to more CO2
But it is a very effective driver of warming.
The other thing about it is that we can control it.
And that's one of the things which gives the lie to your idea

"it's inherently chaotic and driven by something we can't measure, predict or control".

The other things that make it clear that you are talking nonsense are that we can measure it and we can predict it.
So you were plainly wrong on all three counts.
The fact that the predictions are imperfect isn't important; I presume you check the weather forecast before you fly. If you don't think we can predict it, why do you bother?

If you don't think we can measure it, perhaps you should stop giving talks about it.

BC is usually the first to point out that weather is not climate. It must be past his bedtime!

Actually, I was watching Blakes 7 on a subscription TV service.

However, if I had seen that Evan was talking about people modelling the weather and the climate I would have used my ability to count to two and recognised that he was talking about modelling two separate, though related, things.

[evan_au]

Moderator's note: A tangent on interpreting historical ice cores was split off to "How come the ice core temperature curve always leads the CO2 curve?".

The current thread is based on current climate modeling and is more forward-looking and action-oriented.
- Please post comments in the appropriate thread.

[Timo Meyer]

It is clear that there is damage that we have caused ourselves, but how long does it actually take until planned measures bring our climate back to a healthy and normal climate to some extent?

[alancalverd]

Is it clear? The Arctic region was a lot warmer 500 years ago.

[Bored chemist]

Is it clear? The Arctic region was a lot warmer 500 years ago.

Well...
https://en.wikipedia.org/wiki/Medieval_Warm_Period#/media/File:2000+_year_global_temperature_including_Medieval_Warm_Period_and_Little_Ice_Age_-_Ed_Hawkins.svg

[alancalverd]

Receding glaciers are revealing vegetation that was active (and not covered with ice) around 500 years ago.

Caution! Evidence can harm your preconceptions!

[chemhat1999]

Well i`m not sure whether it is important, how warm or cold the poles were 500 yrs ago...
Of course that is an interesting topic, but not necessarily for this thread
The problem, as suggested by the graph from Bored Chemist, is quite dire and lies in the present.