Global warming: Regional climate change impacts
Posted: Sat Jan 10, 2015 12:30 pm
Increasingly I get "requests" (emails, PMs, blog comments) for forecasts of future global warming impacts that have a local orientation: "Sure the global average is going heat up by 2, 4, or even 6+ degrees(*), but what does that mean for me living in coastal South Carolina now and in 50 years---what if I move inland?" and so on.
(*) When people [scientists!] are talking degrees, they're talking Celcius (or Kelvin, same thing), not Fahrenheit. The conversion factor is 1.8F=1C.
Over the past 5-10 years, research of regional impacts have grown in focus. It's important to keep in mind that really grokking this still require substantial amounts of practical thinking since the impacts are wide, very interconnected, and depend on local features (hey, it's just like ERE). In other words, you may have to fill in some of the finer resolution blanks for your particular neighborhood/city/region. This is no different that buying or selling real estate though knowing which are the good hoods and which are the bad. The scientific forecasts just suggest you use a different perspective (e.g. considering where what kind of power plant supply your electricity, where the future flood levels are in relation to the transport supply lines, and how sensitive the local economy is to "nature" instead of nearby parks, access to supermarkets, ... )
One example to ponder. In 2003 there was an unprecedented heatwave in central Europe with temperatures reaching 40C (100F+) featuring high humidity. It lasted a couple of months. Tens of thousands, mainly elderly, died from heat stress. The situation was that Europe at the time was not big on A/C so few people had it. Those who did have it eventually got squeezed too as rivers heated up so much that power plants could no longer run their turbines because of a lack of cooling water, so no electricity to run your A/C even if you had one. Point being, not only did you have to be aware of the extreme weather risk due to the climate change (already underway), you also had to be prepared and own an A/C (which not many people did), AND you had to be prepared to compensate for losing electric power. Thus you would have to put three largely disconnected facts together on your own in order to go through that event without personal impact.
Second example to ponder. in 1995 there was a heatwave in Chicago that killed 750 people. Again, this was people who couldn't afford A/C and who were too old/unfit to sustain the heat stress. What's interesting here is the difference in death toll between North Lawndale (the war zone ghetto---I would not ride a bike through that area) and South Lawndale (the not so waring ghetto----I have ridden my bike through that area) despite being right next to each other. In NL people kept their windows closed at night and didn't go out for fear of crime. SL also has crime but unlike NL it also has shops and supermarkets and---very importantly---enough of a community that people could and would venture into supermarkets and cool off(**) without being hassled for loitering. Again, you have to put some largely disconnected dots into the right perspective.
(**) In heat waves, it's not the heat per se that kills but the cumulative exhaustion if you can't get any relief whatsoever over a long time period.
Onto the forecasts ... The greatest uncertainty wrt the forecasts is not the science but the fact that it is "hard" to predict human politics. Basically, you're looking at three variables:
1) Location (you can personally change this by relocating)
2) Total human emissions (not much you can do about this personally. This would require international agreements.)
3) Timeline (not so important if you'll likely be dead before 2020; quite important from an ERE perspective if say you're 25 today and want to figure out how to deal with the impacts of the 2050s or 2070s(%) or you have children and want to set them up in a good location; also in terms of how much reaction time you have ... should you be dealing with this problem now or in 20 years, etc.)
(%) For example, your plan for your old age (in 2060) might involve living in a studio apartment in Los Angeles near the beach while investing in local real estate for your income. In light of the forecasts, this would be a tremendously stupid idea.
Scientifically the uncertainty in (2) is dealt with by running scenarios. Basically, multiple models are run with the different human emission pathways: If this and that agreement is reached, then the world will look like this in region X at time Y. Hence, "all" you gotta do is to input what you believe humanity will be doing in terms of emissions and you will get a forecast in terms of time and place.
The current scientific modelling has be standardized over 4 different scenarios, called RCP2.6, RCP4.5, RCP6, and RCP8.5.
http://en.wikipedia.org/wiki/Representa ... n_Pathways
That is... for each emissions scenario, there is a corresponding prediction of the future climate that results from this choice of behavior. These are considered to be _equally_ representative of what humanity might do, that is, we can choose to get into the RCP2.6 by choosing one course just as we can get into RCP8.5 by choosing another. More about that later.
These numbers are not temperatures but radiative forcings (so don't get confused!). However, they can be translated into temperatures and many other books do so. The temperatures will be attained in a somewhat linearly fashion between now and the year 2100. E.g. if the year 2100 temperature is 3C (globally, regional temps can be much higher or lower), then that translates into 3C/85years = 0.35C/decade trend(!) and so on. Many less technical sources tend to talk about things in terms of temperatures instead, so here's the rough translation. RCP2.6 is the "one degree world", RCP4.5 is the "two degree world", RCP6 is the "three degree world" and RCP8.5 is the "four degree world".
You should also know that forecasts are not exact but rather come in ranges with ascribed probability. Thus a "four degree" prediction means that the expectation value (the mean temperature) of a range of models that investigate the nonlinear (crash and jump behavior) behavior slightly different parameters and that the actual outcomes fall on a probability curve.
If you've spent any time looking at SWR and portfolios at firecalc you should be familiar with the idea. Unlike firecalc, scientists use physics to run their models instead of historical returns. What this means is that even if we, say, choose an emission pathway that leads to RCP4.5, there's some probability that we'll end up in the scenarios that are better described by 2.6 or 6. We might be lucky or unlucky in that regard. This is similar to firecalc having the final outcome being dependent on a particularly good or bad thing happening or not happening.
The astute reader might ask, where is the "zero degree" scenario. Well, that one is now gone. It's history. Based on our [global] lack of action over the past 20-30 years we are locked into at least 1 degree. If we had done something 20 years ago, we could have chosen zero degrees, but this option is no longer there.
Which scenario you chose to look at depends on your personal risk profile and time horizon. First, the two degree world in 2100 will look like what the four degree world will look like in 2050, so your time horizon matters. Second, you might not care about certain risks from climate change (e.g. dying from heat stress) just like many people don't care about other health risks (e.g. dying from cancer due to smoking). The point is, it's possible to forecast with high precision (even 50 year old forecasts are quite on the dot wrt the present climate) what will happen and when it well. You can choose to use this information if you want.
In terms of predicting scenarios, I can tell you, however, that business as usual will lead to RCP8.5 or the four degrees (or more) worlds AND that this is one humanity is currently tracking. The agreements that politicians (US and China) most recently have agreed to maybe agree on some time in the future will send us onto the RCP6 scenario. So that's where that stands right now. Based on my understanding on politics, etc. that's where I'd put MY money, but you can put yours on more hopeful RCPs in which the world agrees to a stronger cut than it currently does. Again, up to you.
So this is the background for understanding the following:
First, I recommend actually understanding the science. This provides a much better foundation for understanding the predictions. Based on the other CC thread, it's clear that most people are mostly ignorant about the science.
The quick&easy way is this book
http://www.amazon.com/The-Cartoon-Intro ... 610914384/
It's a cartoon but that makes it a quick read, but it provides a solid basis, and it'll resolve some of the stupider objections/misunderstandings many have.
For the global impacts, I suggest this book. Again, it's in Celcius not Fahrenheit. This is useful to realize that 3C doesn't just mean a balmier summer to be solved by just cranking up the AC to compensate for the extra 5.4F degrees.
http://www.amazon.com/Six-Degrees-Futur ... 426203853/
Note that this was written in 2007. Towards the end he talks about how immediate action can avoid the 400ppm scenario. As of last year (2014), we have now crossed 400ppm.
Here are the meat and potatoes for the US where you can look up your state. These predictions are for the RCP2.6 and 4.5 scenarios though.
http://www.ucsusa.org/global_warming/sc ... hange.html
they are based on
http://www.globalchange.gov/browse/fede ... n-modeling
(plenty of reading there!)
This is a global map where you can see overall impacts AND local temperatures. That allows you to translate RCP8.5's 4 degrees global average into local degrees. For example, for Chicago, that 14 degrees Fahrenheit. (Inland heats much more than coastal).
http://www.metoffice.gov.uk/climate-gui ... e-rise/map
For the ultimate resource on impacts, go to
http://www.ipcc.ch/report/ar5/wg2/
You'd want to go to the references listed here as this is a review article.
And finally, for keeping track of the likely scenarios, here are the total carbon budgets/emissions limits (this much and no more) for various scenarios and the probability of staying inside them
https://docs.google.com/spreadsheets/d/ ... edit#gid=0
PS: I request that this thread stay on the topic of discussing impacts only. We already have another CC thread for discussing climate science or/and displaying one's ignorance thereof up to and even including basic physics. I will move off-topic posts to that thread.
(*) When people [scientists!] are talking degrees, they're talking Celcius (or Kelvin, same thing), not Fahrenheit. The conversion factor is 1.8F=1C.
Over the past 5-10 years, research of regional impacts have grown in focus. It's important to keep in mind that really grokking this still require substantial amounts of practical thinking since the impacts are wide, very interconnected, and depend on local features (hey, it's just like ERE). In other words, you may have to fill in some of the finer resolution blanks for your particular neighborhood/city/region. This is no different that buying or selling real estate though knowing which are the good hoods and which are the bad. The scientific forecasts just suggest you use a different perspective (e.g. considering where what kind of power plant supply your electricity, where the future flood levels are in relation to the transport supply lines, and how sensitive the local economy is to "nature" instead of nearby parks, access to supermarkets, ... )
One example to ponder. In 2003 there was an unprecedented heatwave in central Europe with temperatures reaching 40C (100F+) featuring high humidity. It lasted a couple of months. Tens of thousands, mainly elderly, died from heat stress. The situation was that Europe at the time was not big on A/C so few people had it. Those who did have it eventually got squeezed too as rivers heated up so much that power plants could no longer run their turbines because of a lack of cooling water, so no electricity to run your A/C even if you had one. Point being, not only did you have to be aware of the extreme weather risk due to the climate change (already underway), you also had to be prepared and own an A/C (which not many people did), AND you had to be prepared to compensate for losing electric power. Thus you would have to put three largely disconnected facts together on your own in order to go through that event without personal impact.
Second example to ponder. in 1995 there was a heatwave in Chicago that killed 750 people. Again, this was people who couldn't afford A/C and who were too old/unfit to sustain the heat stress. What's interesting here is the difference in death toll between North Lawndale (the war zone ghetto---I would not ride a bike through that area) and South Lawndale (the not so waring ghetto----I have ridden my bike through that area) despite being right next to each other. In NL people kept their windows closed at night and didn't go out for fear of crime. SL also has crime but unlike NL it also has shops and supermarkets and---very importantly---enough of a community that people could and would venture into supermarkets and cool off(**) without being hassled for loitering. Again, you have to put some largely disconnected dots into the right perspective.
(**) In heat waves, it's not the heat per se that kills but the cumulative exhaustion if you can't get any relief whatsoever over a long time period.
Onto the forecasts ... The greatest uncertainty wrt the forecasts is not the science but the fact that it is "hard" to predict human politics. Basically, you're looking at three variables:
1) Location (you can personally change this by relocating)
2) Total human emissions (not much you can do about this personally. This would require international agreements.)
3) Timeline (not so important if you'll likely be dead before 2020; quite important from an ERE perspective if say you're 25 today and want to figure out how to deal with the impacts of the 2050s or 2070s(%) or you have children and want to set them up in a good location; also in terms of how much reaction time you have ... should you be dealing with this problem now or in 20 years, etc.)
(%) For example, your plan for your old age (in 2060) might involve living in a studio apartment in Los Angeles near the beach while investing in local real estate for your income. In light of the forecasts, this would be a tremendously stupid idea.
Scientifically the uncertainty in (2) is dealt with by running scenarios. Basically, multiple models are run with the different human emission pathways: If this and that agreement is reached, then the world will look like this in region X at time Y. Hence, "all" you gotta do is to input what you believe humanity will be doing in terms of emissions and you will get a forecast in terms of time and place.
The current scientific modelling has be standardized over 4 different scenarios, called RCP2.6, RCP4.5, RCP6, and RCP8.5.
http://en.wikipedia.org/wiki/Representa ... n_Pathways
That is... for each emissions scenario, there is a corresponding prediction of the future climate that results from this choice of behavior. These are considered to be _equally_ representative of what humanity might do, that is, we can choose to get into the RCP2.6 by choosing one course just as we can get into RCP8.5 by choosing another. More about that later.
These numbers are not temperatures but radiative forcings (so don't get confused!). However, they can be translated into temperatures and many other books do so. The temperatures will be attained in a somewhat linearly fashion between now and the year 2100. E.g. if the year 2100 temperature is 3C (globally, regional temps can be much higher or lower), then that translates into 3C/85years = 0.35C/decade trend(!) and so on. Many less technical sources tend to talk about things in terms of temperatures instead, so here's the rough translation. RCP2.6 is the "one degree world", RCP4.5 is the "two degree world", RCP6 is the "three degree world" and RCP8.5 is the "four degree world".
You should also know that forecasts are not exact but rather come in ranges with ascribed probability. Thus a "four degree" prediction means that the expectation value (the mean temperature) of a range of models that investigate the nonlinear (crash and jump behavior) behavior slightly different parameters and that the actual outcomes fall on a probability curve.
If you've spent any time looking at SWR and portfolios at firecalc you should be familiar with the idea. Unlike firecalc, scientists use physics to run their models instead of historical returns. What this means is that even if we, say, choose an emission pathway that leads to RCP4.5, there's some probability that we'll end up in the scenarios that are better described by 2.6 or 6. We might be lucky or unlucky in that regard. This is similar to firecalc having the final outcome being dependent on a particularly good or bad thing happening or not happening.
The astute reader might ask, where is the "zero degree" scenario. Well, that one is now gone. It's history. Based on our [global] lack of action over the past 20-30 years we are locked into at least 1 degree. If we had done something 20 years ago, we could have chosen zero degrees, but this option is no longer there.
Which scenario you chose to look at depends on your personal risk profile and time horizon. First, the two degree world in 2100 will look like what the four degree world will look like in 2050, so your time horizon matters. Second, you might not care about certain risks from climate change (e.g. dying from heat stress) just like many people don't care about other health risks (e.g. dying from cancer due to smoking). The point is, it's possible to forecast with high precision (even 50 year old forecasts are quite on the dot wrt the present climate) what will happen and when it well. You can choose to use this information if you want.
In terms of predicting scenarios, I can tell you, however, that business as usual will lead to RCP8.5 or the four degrees (or more) worlds AND that this is one humanity is currently tracking. The agreements that politicians (US and China) most recently have agreed to maybe agree on some time in the future will send us onto the RCP6 scenario. So that's where that stands right now. Based on my understanding on politics, etc. that's where I'd put MY money, but you can put yours on more hopeful RCPs in which the world agrees to a stronger cut than it currently does. Again, up to you.
So this is the background for understanding the following:
First, I recommend actually understanding the science. This provides a much better foundation for understanding the predictions. Based on the other CC thread, it's clear that most people are mostly ignorant about the science.
The quick&easy way is this book
http://www.amazon.com/The-Cartoon-Intro ... 610914384/
It's a cartoon but that makes it a quick read, but it provides a solid basis, and it'll resolve some of the stupider objections/misunderstandings many have.
For the global impacts, I suggest this book. Again, it's in Celcius not Fahrenheit. This is useful to realize that 3C doesn't just mean a balmier summer to be solved by just cranking up the AC to compensate for the extra 5.4F degrees.
http://www.amazon.com/Six-Degrees-Futur ... 426203853/
Note that this was written in 2007. Towards the end he talks about how immediate action can avoid the 400ppm scenario. As of last year (2014), we have now crossed 400ppm.
Here are the meat and potatoes for the US where you can look up your state. These predictions are for the RCP2.6 and 4.5 scenarios though.
http://www.ucsusa.org/global_warming/sc ... hange.html
they are based on
http://www.globalchange.gov/browse/fede ... n-modeling
(plenty of reading there!)
This is a global map where you can see overall impacts AND local temperatures. That allows you to translate RCP8.5's 4 degrees global average into local degrees. For example, for Chicago, that 14 degrees Fahrenheit. (Inland heats much more than coastal).
http://www.metoffice.gov.uk/climate-gui ... e-rise/map
For the ultimate resource on impacts, go to
http://www.ipcc.ch/report/ar5/wg2/
You'd want to go to the references listed here as this is a review article.
And finally, for keeping track of the likely scenarios, here are the total carbon budgets/emissions limits (this much and no more) for various scenarios and the probability of staying inside them
https://docs.google.com/spreadsheets/d/ ... edit#gid=0
PS: I request that this thread stay on the topic of discussing impacts only. We already have another CC thread for discussing climate science or/and displaying one's ignorance thereof up to and even including basic physics. I will move off-topic posts to that thread.
. Presuming those sort of heat waves become more common, some city dwellers in northern cities will have to change their behavior or move to cities even further north.