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Climate Sensitivity


Climate Sensitivity07-04-2017 21:40
student33
☆☆☆☆☆
(15)
Hi there - I'm new to climate change and am trying to get my around how it works.

I have a question:

The IPCC in its AR5 use 4 RCPs to project future surface temperatures to the future period 2100. These scenarios are named after values of radiative forcing.

I understand climate sensitivity equation (as given by the IPCC) as:

∆T=∆F x λ x (1-λ c)^(-1)

where ∆F is the radiative forcing.

My question is how do the RCP scenarios 'fit' into climate sensitivity. How do we get from climate sensitivity (which I am assuming to be the fundamental calculation, to the RCP scenarios which project future temperatures - how do the RCPS connect to climate sensitivity - what is the piece of theory / knowledge / that bridges the two things together)?

What is the purpose of climate sensitivity in relation to the IPCC graphs of future temperature projections? How does it fit into projecting these future temperatures? Are calculations of climate sensitivity NEEDED in order to calculate future temperatures, or is it only the radiative forcing ∆F part of the equation that is needed to do so?

Thanks.
Edited on 07-04-2017 21:56
07-04-2017 22:17
Tim the plumber
★★★★☆
(1295)
Climate sensitivity is the amount of additional heat energy going into the energy budget at the surface of the earth. Although there are those who call the final balance temperature produced by this additional energy the sensitivity.

The simple bit is the number of increased Watts per square meter from a doubling of CO2. The general number quoted is about 3.4 W/m2. This is contentious. Lots of debate, lots of differing views. The 3.4 is the IPCC/consensus number.

3.4W/m2 is about +3c final temperature balance.

The complex bit is that the response time for the world is so slow that it will be many many centuries before we get to the balance mostly because of the massive heat capacity of the oceans. Also how do we know what changes the oceans are still dealing with from 500 years ago? All starting to get very very complex.

The next complex thing to hit the fan is that the IPCC claims that there are positive feedback effects which will magnify the inital warming. Lots more debate and no evidecne of such in actual action ever gets presented.

The big problem for the IPCC et al is that they predicted in the early 2000's a rapid warming and no such warming has actually happened. The temperature has been shockingly stable. Possibly a slight warming last year but overall nothing.

Edited on 07-04-2017 22:18
07-04-2017 22:24
student33
☆☆☆☆☆
(15)
Tim the plumber wrote:
Climate sensitivity is the amount of additional heat energy going into the energy budget at the surface of the earth. Although there are those who call the final balance temperature produced by this additional energy the sensitivity.

The simple bit is the number of increased Watts per square meter from a doubling of CO2. The general number quoted is about 3.4 W/m2. This is contentious. Lots of debate, lots of differing views. The 3.4 is the IPCC/consensus number.

3.4W/m2 is about +3c final temperature balance.

The complex bit is that the response time for the world is so slow that it will be many many centuries before we get to the balance mostly because of the massive heat capacity of the oceans. Also how do we know what changes the oceans are still dealing with from 500 years ago? All starting to get very very complex.

The next complex thing to hit the fan is that the IPCC claims that there are positive feedback effects which will magnify the inital warming. Lots more debate and no evidecne of such in actual action ever gets presented.

The big problem for the IPCC et al is that they predicted in the early 2000's a rapid warming and no such warming has actually happened. The temperature has been shockingly stable. Possibly a slight warming last year but overall nothing.


Hi Tim - Thanks for this great reply. (It's reaffirmed what I already kinda know about the climate sensitivity equation and how the different parts that make it up are disputed by the community). The equation is not really a problem for me as I kinda understand it, and how the parts that make it up work.

I'm just trying to understand how climate sensitivity fits into the RCPs to project future temperatures - what is the link between climate sensitivity and how the RCPs project future temperatures.

Thanks.
Edited on 07-04-2017 22:25
07-04-2017 22:43
student33
☆☆☆☆☆
(15)
Tim the plumber wrote:
Climate sensitivity is the amount of additional heat energy going into the energy budget at the surface of the earth. Although there are those who call the final balance temperature produced by this additional energy the sensitivity.

The simple bit is the number of increased Watts per square meter from a doubling of CO2. The general number quoted is about 3.4 W/m2. This is contentious. Lots of debate, lots of differing views. The 3.4 is the IPCC/consensus number.

3.4W/m2 is about +3c final temperature balance.

The complex bit is that the response time for the world is so slow that it will be many many centuries before we get to the balance mostly because of the massive heat capacity of the oceans. Also how do we know what changes the oceans are still dealing with from 500 years ago? All starting to get very very complex.

The next complex thing to hit the fan is that the IPCC claims that there are positive feedback effects which will magnify the inital warming. Lots more debate and no evidecne of such in actual action ever gets presented.

The big problem for the IPCC et al is that they predicted in the early 2000's a rapid warming and no such warming has actually happened. The temperature has been shockingly stable. Possibly a slight warming last year but overall nothing.


Hi Tim - From what I know and read so far, the fact that the warming projected by the IPCC did not occur was due to (i) a weak Sun (ii) a few major volcanic events (iii) pollution from particulate (PM) matter, especially from an industrialising China - all of which are negative forcings not included in the IPCC's climate sensitivity equation.
Edited on 07-04-2017 22:47
07-04-2017 23:38
Tim the plumber
★★★★☆
(1295)
student33 wrote:
Tim the plumber wrote:
Climate sensitivity is the amount of additional heat energy going into the energy budget at the surface of the earth. Although there are those who call the final balance temperature produced by this additional energy the sensitivity.

The simple bit is the number of increased Watts per square meter from a doubling of CO2. The general number quoted is about 3.4 W/m2. This is contentious. Lots of debate, lots of differing views. The 3.4 is the IPCC/consensus number.

3.4W/m2 is about +3c final temperature balance.

The complex bit is that the response time for the world is so slow that it will be many many centuries before we get to the balance mostly because of the massive heat capacity of the oceans. Also how do we know what changes the oceans are still dealing with from 500 years ago? All starting to get very very complex.

The next complex thing to hit the fan is that the IPCC claims that there are positive feedback effects which will magnify the inital warming. Lots more debate and no evidecne of such in actual action ever gets presented.

The big problem for the IPCC et al is that they predicted in the early 2000's a rapid warming and no such warming has actually happened. The temperature has been shockingly stable. Possibly a slight warming last year but overall nothing.


Hi Tim - From what I know and read so far, the fact that the warming projected by the IPCC did not occur was due to (i) a weak Sun (ii) a few major volcanic events (iii) pollution from particulate (PM) matter, especially from an industrialising China - all of which are negative forcings not included in the IPCC's climate sensitivity equation.


They strike me as after the fact excusses.

Especially the volcanoe thing as there has only been the one big event, in news terms, from Iceland and that was just because it stopped the aircraft. I don't see this period, 1998 to 2017, as more volcanically active than any other. Maybe you have better info?

The CO2 has risen much more sharply that the IPCC's worste case and yet we have had less warming than their least effect case. I don't know enough to say if they have it totally worng on this or not but the results are against them being any good.....

The bit about all this AGW thing is that when I ask for what the bad effects of a slightly warmer world would be there is never a decent answer. More rain fall, slightly warmer, longer growing seasons all strike me as good things.
08-04-2017 04:04
Surface Detail
★★★★☆
(1673)
student33 wrote:
Hi there - I'm new to climate change and am trying to get my around how it works.

I have a question:

The IPCC in its AR5 use 4 RCPs to project future surface temperatures to the future period 2100. These scenarios are named after values of radiative forcing.

I understand climate sensitivity equation (as given by the IPCC) as:

∆T=∆F x λ x (1-λ c)^(-1)

where ∆F is the radiative forcing.

My question is how do the RCP scenarios 'fit' into climate sensitivity. How do we get from climate sensitivity (which I am assuming to be the fundamental calculation, to the RCP scenarios which project future temperatures - how do the RCPS connect to climate sensitivity - what is the piece of theory / knowledge / that bridges the two things together)?

What is the purpose of climate sensitivity in relation to the IPCC graphs of future temperature projections? How does it fit into projecting these future temperatures? Are calculations of climate sensitivity NEEDED in order to calculate future temperatures, or is it only the radiative forcing ∆F part of the equation that is needed to do so?

Thanks.

The RPC (Representative Concentration Pathway) scenarios are simply four possible ways in which greenhouse concentration could develop over the coming years. Each RPC is based on a different assumption of human behaviour over the coming years, ranging from RCP 2.6 (immediate drastic measures to curb GHG emissions) to RCP 8.5 (business as usual). The labels represent the radiative forcing (difference between incoming and outgoing radiation) to be expected for each scenario by the year 2100. The forcings are calculated from the expected levels of GHGs in the atmosphere and other factors under each scenario.

It is only then that climate sensitivity (λ) comes into play. This is the link that gives the final temperature change corresponding to each forcing and is probably where the most uncertainty lies. A low climate sensitivity would mean that a large forcing (from e.g. GHGs, changes in land use) would only cause a small temperature change; a large climate sensitivity would lead to a large temperature change for a relatively small forcing.

Note, though, that climate sensitivity is often expressed not in terms of the forcing required to raise temperature by one degree, but rather in the temperature rise resulting from the equivalent of doubling the CO2 concentration. The IPCC currently estimates this to be about 3°C.
08-04-2017 04:42
Into the Night
★★★★★
(8592)
Surface Detail wrote:
student33 wrote:
Hi there - I'm new to climate change and am trying to get my around how it works.

I have a question:

The IPCC in its AR5 use 4 RCPs to project future surface temperatures to the future period 2100. These scenarios are named after values of radiative forcing.

I understand climate sensitivity equation (as given by the IPCC) as:

∆T=∆F x λ x (1-λ c)^(-1)

where ∆F is the radiative forcing.

My question is how do the RCP scenarios 'fit' into climate sensitivity. How do we get from climate sensitivity (which I am assuming to be the fundamental calculation, to the RCP scenarios which project future temperatures - how do the RCPS connect to climate sensitivity - what is the piece of theory / knowledge / that bridges the two things together)?

What is the purpose of climate sensitivity in relation to the IPCC graphs of future temperature projections? How does it fit into projecting these future temperatures? Are calculations of climate sensitivity NEEDED in order to calculate future temperatures, or is it only the radiative forcing ∆F part of the equation that is needed to do so?

Thanks.

The RPC (Representative Concentration Pathway) scenarios are simply four possible ways in which greenhouse concentration could develop over the coming years. Each RPC is based on a different assumption of human behaviour over the coming years, ranging from RCP 2.6 (immediate drastic measures to curb GHG emissions) to RCP 8.5 (business as usual). The labels represent the radiative forcing (difference between incoming and outgoing radiation) to be expected for each scenario by the year 2100. The forcings are calculated from the expected levels of GHGs in the atmosphere and other factors under each scenario.

It is only then that climate sensitivity (λ) comes into play. This is the link that gives the final temperature change corresponding to each forcing and is probably where the most uncertainty lies. A low climate sensitivity would mean that a large forcing (from e.g. GHGs, changes in land use) would only cause a small temperature change; a large climate sensitivity would lead to a large temperature change for a relatively small forcing.

Note, though, that climate sensitivity is often expressed not in terms of the forcing required to raise temperature by one degree, but rather in the temperature rise resulting from the equivalent of doubling the CO2 concentration. The IPCC currently estimates this to be about 3°C.


The IPCC can 'estimate' all it wants. It can use manufactured data all it wants. It doesn't change the violations of physics in the 'greenhouse' Holy Gas argument.

Damn good thing science isn't defined by a political group like the IPCC.


The Parrot Killer




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