Can We Start Small?

[rygar]

I am not well versed on the debate in the least bit, but I do find the topic terribly interesting. It's incredible we have a global issue staring us in the face that could truly turn into a disaster in the long run, yet we really can't get agreement in the scientific community. Lets hope for a consensus in the near future.

Anyway, I was hoping to start small with a simple question. How much has the earth's temperature changed in last 10 years? Last 20? Is there at least agreement from both sides in this matter?

If there is agreement, at what point do the two sides diverge? If there is not agreement, well, if we can't agree about our immediate past how can we agree on the issue at large?

[dabize]

I am not well versed on the debate in the least bit, but I do find the topic terribly interesting. It's incredible we have a global issue staring us in the face that could truly turn into a disaster in the long run, yet we really can't get agreement in the scientific community. Lets hope for a consensus in the near future.

Anyway, I was hoping to start small with a simple question. How much has the earth's temperature changed in last 10 years? Last 20? Is there at least agreement from both sides in this matter?

If there is agreement, at what point do the two sides diverge? If there is not agreement, well, if we can't agree about our immediate past how can we agree on the issue at large?

There is virtually complete scientific consensus that AGW exists, is already becoming a serious problem already in certain places (e.g. Tuvalu, southwestern Australia), and will become increasingly serious for billions of people this century. This link should serve as a start for self-education on the subject - I have posted some others as well, as have some of the serious posters here.

http://www.realclimate.org/index.php/archives/2007/05/start-here/

[skierinvermont]

There already is a scientific consensus. Unless you believe there is a conspiracy theory to keep anti-AGW work from passing peer-review.

To answer your question.. the last 10 years have warmed about .10C/decade. The last 20 years have been warming around .2C/decade. It's simply a matter of doing the calculation. Also you have to be careful because the 10 year trend can be affected depending on what ENSO state you start and end in.

Generally I believe if you want to know how much the surface has warmed, I believe it is best to take an average of GISS+HadCRUT between 60S and 60N, and then use satellite data or model reanalysis data to infill the poles and create a spatially weighted average. This removes the frequent objection that GISS extrapolates the poles, and the objection that HadCRUT leaves the poles out entirely.

[WeatherRusty]

I am not well versed on the debate in the least bit, but I do find the topic terribly interesting. It's incredible we have a global issue staring us in the face that could truly turn into a disaster in the long run, yet we really can't get agreement in the scientific community. Lets hope for a consensus in the near future.

Anyway, I was hoping to start small with a simple question. How much has the earth's temperature changed in last 10 years? Last 20? Is there at least agreement from both sides in this matter?

If there is agreement, at what point do the two sides diverge? If there is not agreement, well, if we can't agree about our immediate past how can we agree on the issue at large?

Being in total agreement with the first two responses, I will add the following.

The longer term trend represented by the entire instrumental record going back to about the year 1880 reveals a warming of about 0.8C. This is a long term running average, not the result of starting and ending at any particular points.

This warming can be accounted for from two basic sources of energy. An increase in averaged solar output can account for about 0.1C of the warming (prior to 1970). About 0.5C can be attributed to an increase in long lived greenhouse gases such as CO2, CH4 and N2O aiding in the delay of thermal radiation loss from Earth's surface. The remainder from everything else combined.

EDIT:

For anyone interested in a detailed explanation of the physics pertaining to the greenhouse effect check out the following link.

See Here

[Alpha5]

I am not well versed on the debate in the least bit, but I do find the topic terribly interesting. It's incredible we have a global issue staring us in the face that could truly turn into a disaster in the long run, yet we really can't get agreement in the scientific community. Lets hope for a consensus in the near future.

Anyway, I was hoping to start small with a simple question. How much has the earth's temperature changed in last 10 years? Last 20? Is there at least agreement from both sides in this matter?

If there is agreement, at what point do the two sides diverge? If there is not agreement, well, if we can't agree about our immediate past how can we agree on the issue at large?

Satellite records only go back to 1979

[skierinvermont]

Satellite records only go back to 1979

You know the primary reason for the sinusoidal nature of that graph is the drop from 1980-1985. If you cut off 1980-1985 and then fit a sin curve to it, it would be a much more linear function. The line drawn actually doesn't fit the last decade very well but it is forced into that shape by the shape of the previous 20 years.

[tacoman25]

You know the primary reason for the sinusoidal nature of that graph is the drop from 1980-1985. If you cut off 1980-1985 and then fit a sin curve to it, it would be a much more linear function. The line drawn actually doesn't fit the last decade very well but it is forced into that shape by the shape of the previous 20 years.

Another way to look at it: the main reason the graph looks like that is that there was significantly more warming from the mid 1980s to the mid 1990s than the past decade.

[Jonger]

Satellite records only go back to 1979

It sucks that satallite records began at the tail end of a cool period.

[skierinvermont]

Another way to look at it: the main reason the graph looks like that is that there was significantly more warming from the mid 1980s to the mid 1990s than the past decade.

No the main reason why a sin curve fits is the decline from 1979 to 1985. If you got rid of that period, the sin curve would be much more linear and would still be increasing this decade. Instead, because 1979-1985 showed cooling, the sin curve begins to replicate that cooling during this decade even though we have not been cooling or flatlining.

[tacoman25]

No the main reason why a sin curve fits is the decline from 1979 to 1985. If you got rid of that period, the sin curve would be much more linear and would still be increasing this decade. Instead, because 1979-1985 showed cooling, the sin curve begins to replicate that cooling during this decade even though we have not been cooling or flatlining.

So the fact that warming has decelerated over the past decade or so has nothing to do with the curve?

Also, the two big volcanic eruptions (especially Pinatubo) clearly played a role in making the graph less linear.

[WeatherRusty]

It sucks that satallite records began at the tail end of a cool period.

That's not true at all. The mid 20th century was as warm as at anytime up till then during that century. Temperature rise halted and maybe fell only slightly, but the period mid century was warm compared to early century.

[Jonger]

I wonder what are the chances of just geoengineering CO2 right out of the atmosphere.

Doing so can ensure the removal of CO2 to bring back pre-industrial era levels and not plunge the world into another medieval period of starvation and disease. Both which would result from attempting to utilize 2011 alternative energy and run the planet without CO2 emissions.

Meaning... we are 5% of the way there to replacing fossil fuels and not destroying the only sentient life forms civilization.

[Jonger]

That's not true at all. The mid 20th century was as warm as at anytime up till then during that century. Temperature rise halted and maybe fell only slightly, but the period mid century was warm compared to early century.

I hardly trust any recorded data before WW2 on a large scale. Local temps I buy into... Widescale and outside of cities... not a chance.

[superjames1992]

If we seriously wanted to do something about AGW, we should have started 30 years ago. I don't think there is much we can do at this point, especially with the non-industrialized world pumping out increasing amounts of CO2 everyday. First-world countries' CO2 output has not increased much in the last few years, but non-industrialized nations' CO2 output is skyrocketing with no end in sight.

[turtlehurricane]

Temp changes on the scale of 10-20 years are insignificant when it comes to climate. Hence all the confusion from both sides.

[LocoAko]

Temp changes on the scale of 10-20 years are insignificant when it comes to climate. Hence all the confusion from both sides.

I don't see both sides confused about it... it is largely one side. -_-

[skierinvermont]

So the fact that warming has decelerated over the past decade or so has nothing to do with the curve?

Also, the two big volcanic eruptions (especially Pinatubo) clearly played a role in making the graph less linear.

Of course that is part of it, but part of the reason the sin curve flatlines at the end has nothing to do with temperatures the last decade and is just a reflection of what happened 1979-1985 (which incidentally RSS does not agree on).

[skierinvermont]

I hardly trust any recorded data before WW2 on a large scale. Local temps I buy into... Widescale and outside of cities... not a chance.

That's because you are not familiar with the stations used and what constitutes an adequate spatial sampling.

[skierinvermont]

If we seriously wanted to do something about AGW, we should have started 30 years ago. I don't think there is much we can do at this point, especially with the non-industrialized world pumping out increasing amounts of CO2 everyday. First-world countries' CO2 output has not increased much in the last few years, but non-industrialized nations' CO2 output is skyrocketing with no end in sight.

I think there is plenty we can do. You have to remember the warming scenarios usually bantered about are based on fairly high emissions scenarios where little/no effort is put into emissions reduction and economic and population growth are fairly strong. You also have to remember that the consequences get progressively worse at >2C, >3C, >4C. In fact, the consequences are somewhat exponential in relation to the amount of warming. For example, Greenland will melt much faster at 3C than 2C of warming. At 2C it might not even melt at all or if it did it would be fairly slow (2C is the cutoff), while at 3C of global warming it would melt within a couple hundred years. 4C would probably be even faster. Less+slower sea level rise is MUCH MUCH better than large+fast sea level rise.

Also in terms of species adaptation, 2C of warming will give much more time for adaptation. Also above 2C of warming you start entering into temperatures where present species have never existed. That's not to say that all species will survive at 1.5C of warming because the speed of the warming is so much greater than anything before, but 2.5C is both even faster and above anything modern species have ever experienced and thus likely much worse.

We probably still realistically have the capacity to hold AGW at around 2C, possibly 1.5C if you believe the lower climate sensitivity estimates. This would require the U.S. and Europe to curb there emissions by 20 or 30% over the next 20 years, and for China and the rest of the developing world to grow their's slower than they would otherwise. But it would still allow for China to grow their emissions some.

I agree we don't have much chance of holding warming below 1C without drastic and painful cuts in the U.S. and Europe and without China voluntarily capping their emissions entirely (probably would even have to be cut).

[skierinvermont]

Compare A1B to B1. A1B is 3C of warming, B1 is 1.8C by 2100.

And then compare the GHG emissions scenarios on the right. B1 (green line) still allows for emissions growth. Just not as much as A1B which has fairly rapid emissions growth.

With B1 we can have emissions in 2040 that are 20% greater than today and still end up with only 1.8C of warming (1.5C if climate sensitivity falls on the low side of current estimates).

B2 (blue line) is 2.5C of warming.

[tacoman25]

Of course that is part of it, but part of the reason the sin curve flatlines at the end has nothing to do with temperatures the last decade and is just a reflection of what happened 1979-1985 (which incidentally RSS does not agree on).

Incidentally, RSS also does not agree with your warming trend the past decade.

[Jonger]

That's because you are not familiar with the stations used and what constitutes an adequate spatial sampling.

Ya, because people considered spatial sampling in the 1880s.

I bet 99% of thermometers were in cities that have substantial heat retaining structures built around them. Most settlements in the 1800s are now located within the core center of every city.

[skierinvermont]

Ya, because people considered spatial sampling in the 1880s.

I bet 99% of thermometers were in cities that have substantial heat retaining structures built around them. Most settlements in the 1800s are now located within the core center of every city.

Oh **** you're right. That never occurred to me before. I am embarrassed to have missed something so obvious. I can't believe nobody else thought of that either.

[PhillipS]

Ya, because people considered spatial sampling in the 1880s.

I bet 99% of thermometers were in cities that have substantial heat retaining structures built around them. Most settlements in the 1800s are now located within the core center of every city.

Perhaps you should read the draft reports for the BEST project. The Koch funded study found that Urban Heat Island (UHI) effect , which has been known for a long, long time, has been properly accounted for in the land temperature record. Here is the Global Land Surface Temperature plot from BEST:

As you can see, the long term trend is warming, with a cumulative of about one degree over the past sixty years. Another thing to note is that natural variability (weather and cycles such as ENSO) can cause periods of cooling without affecting the long-term warming trend. This is why climatologists use 30 years as the minimum period for determining climate trends.

So if anybody tries to tell you that global warming has stopped based on a few recent years they are either misinformed, or dishonest - but in either case they're wrong.

[turtlehurricane]

I don't see both sides confused about it... it is largely one side. -_-

10-20 years is in the noise part of the spectrum when it comes to climate, that's all I'm referring to.

AGW from CO2 is real, but so are other factors that we don't have a good handle on. Therefore, a 10-20 year trend doesn't tell us much.