Let's discuss skepticalscience.com's "How do we know more CO2 is causing warming?"

[blizzard1024]

I started this thread to sincerely review what I think is a very important topic for all skeptics (aka "deniers") and 

believers (aka "warmists") alike. When I was in grad school we often were given a paper to read and then

as a class discuss and debate it. In that way, we all learned a lot more than if you just read the paper alone. 

Other people's viewpoints and scientific expertise really helped clarify and point out things that you might

miss or question. 

 

Anyway, let's see how this goes... the website is titled "How do we know more CO2 is causing warming?"

from skepticalscience.com.  I chose the advanced level because I believe people on this forum are in the

advanced level of scientific knowledge(this link better work!!)  

 

http://www.skepticalscience.com/empirical-evidence-for-co2-enhanced-greenhouse-effect-advanced.htm

 

I read through this and the first point that I challenge is:  how do we know that the .8C increase in warming since

1850 is entirely anthropogenic? For their climate sensitivity analysis they use .8C and the current level of

CO2 radiative forcing to rule out that forcing is small from CO2. How do we know that the climate system

was in a state of balance in 1850? On shorter time scales (orbital parameters fairly constant) the climate

has been and always will be changing due to stochastic variations. There is no reason to believe that

it is in equilibrium ever. The same goes for the conservation of energy (since 1850) argument. How do we

know what the natural forcings were and how do we know the natural forcings were not positive at 1850, 1900

or anytime in this period?? 

 

I will stop here. The article is not that long at all. 

[Snow_Miser]

I started this thread to sincerely review what I think is a very important topic for all skeptics (aka "deniers") and 

believers (aka "warmists") alike. When I was in grad school we often were given a paper to read and then

as a class discuss and debate it. In that way, we all learned a lot more than if you just read the paper alone. 

Other people's viewpoints and scientific expertise really helped clarify and point out things that you might

miss or question. 

 

Anyway, let's see how this goes... the website is titled "How do we know more CO2 is causing warming?"

from skepticalscience.com.  I chose the advanced level because I believe people on this forum are in the

advanced level of scientific knowledge(this link better work!!)  

 

http://www.skepticalscience.com/empirical-evidence-for-co2-enhanced-greenhouse-effect-advanced.htm

 

I read through this and the first point that I challenge is:  how do we know that the .8C increase in warming since

1850 is entirely anthropogenic? For their climate sensitivity analysis they use .8C and the current level of

CO2 radiative forcing to rule out that forcing is small from CO2. How do we know that the climate system

was in a state of balance in 1850? On shorter time scales (orbital parameters fairly constant) the climate

has been and always will be changing due to stochastic variations. There is no reason to believe that

it is in equilibrium ever. The same goes for the conservation of energy (since 1850) argument. How do we

know what the natural forcings were and how do we know the natural forcings were not positive at 1850, 1900

or anytime in this period?? 

 

I will stop here. The article is not that long at all. 

 

Great Thread. It's about time that a thread like this was posted about Skeptical Science.

[Snow_Miser]

Here are their arguments for the warming being caused by CO2 in italics:

 

1) CO2 is increasing. This is not disputed.

 

2) CO2 is a Greenhouse Gas.

 

3) CO2 is a Greenhouse Gas. Two and Three are also not disputed.

 

4) Models "prove" that Carbon Dioxide is the cause of the recent warming. This is false, as models are no where even close to modelling some of the fundamental aspects of climate.

 

5) High Climate Sensitivity means that Carbon Dioxide is sufficient to explain recent warming. This is an assumption that does not address all of the uncertainties concerning Climate Sensitivity.

[WeatherRusty]

It is quite certain that solar radiative forcing (TSI) has been very small relative to the anthropogenic forcing since the Maunder Minimum (0.12W/m^2 vrs. 1.6W/m^2). The only other variable which matters is albedo, and since clouds act as feedback to warming and under the presumption of near constant RH, cloudiness shouldn't change that much. Otherwise a small change in low cloud amount due to warming would act as a slight negative feedback, while never being able to negate the original external forcing.

[blizzard1024]

It is quite certain that solar radiative forcing (TSI) has been very small relative to the anthropogenic forcing since the Maunder Minimum (0.12W/m^2 vrs. 1.6W/m^2). The only other variable which matters is albedo, and since clouds act as feedback to warming and under the presumption of near constant RH, cloudiness shouldn't change that much. Otherwise a small change in low cloud amount due to warming would act as a slight negative feedback, while never being able to negate the original external forcing.

 

Let's assume you get a 1% increase in low cloud amount. Also let's assume that the low clouds only affect the albedo (which is uncertain, I admit) but nevertheless,

that is what the latest science suggests, low cloud affects mostly albedo and high clouds affects mostly  radiative forcing to a first approximation. So for

a 1% increase in low cloud amount that equals a net radiative forcing of 2.4W/m2. This is using the 240 w/m2 net outgoing IR which is 1/4 of the TSI and

a starting albedo of 30%. That is larger than the whole human induced radiative forcing of around 1.6 w/m2 as per the IPCC chart. This is huge and of course it could go the

other way too which would further enhance the warming. The fact that we can't accurately measure changing cloud fraction let alone changes in low cloud

amount makes the whole forcing-feedback argument very uncertain. We have to rely on models which don't handle clouds well and produce a constant RH.

This is what the models produce a nearly constant RH. So to believe this you have to have faith in the models. This is where the whole AGW and especially

CAGW theory is on shaky ground  scientifically for me. I don't doubt humans are influencing the climate to some degree, I just have my doubts that there

would be "dangerous" interference with the climate system. 

[WeatherRusty]

Let's assume you get a 1% increase in low cloud amount. Also let's assume that the low clouds only affect the albedo (which is uncertain, I admit) but nevertheless,

that is what the latest science suggests, low cloud affects mostly albedo and high clouds affects mostly  radiative forcing to a first approximation. So for

a 1% increase in low cloud amount that equals a net radiative forcing of 2.4W/m2. This is using the 240 w/m2 net outgoing IR which is 1/4 of the TSI and

a starting albedo of 30%. That is larger than the whole human induced radiative forcing of around 1.6 w/m2 as per the IPCC chart. This is huge and of course it could go the

other way too which would further enhance the warming. The fact that we can't accurately measure changing cloud fraction let alone changes in low cloud

amount makes the whole forcing-feedback argument very uncertain. We have to rely on models which don't handle clouds well and produce a constant RH.

This is what the models produce a nearly constant RH. So to believe this you have to have faith in the models. This is where the whole AGW and especially

CAGW theory is on shaky ground  scientifically for me. I don't doubt humans are influencing the climate to some degree, I just have my doubts that there

would be "dangerous" interference with the climate system. 

 

We agree where the uncertainties lie. Just to complicate things a bit more, the net feedback from clouds rsults from (albedo + greenhouse effect). The more low cloud the greater scattering to space of surface warming SW radiation from cloud tops. The more low cloud the greater the greenhouse effect. On balance, the net of low cloud is thought to result in negative forcing as the climate warms.

[csnavywx]

Let's assume you get a 1% increase in low cloud amount. Also let's assume that the low clouds only affect the albedo (which is uncertain, I admit) but nevertheless,

that is what the latest science suggests, low cloud affects mostly albedo and high clouds affects mostly  radiative forcing to a first approximation. So for

a 1% increase in low cloud amount that equals a net radiative forcing of 2.4W/m2. This is using the 240 w/m2 net outgoing IR which is 1/4 of the TSI and

a starting albedo of 30%. That is larger than the whole human induced radiative forcing of around 1.6 w/m2 as per the IPCC chart. This is huge and of course it could go the

other way too which would further enhance the warming. The fact that we can't accurately measure changing cloud fraction let alone changes in low cloud

amount makes the whole forcing-feedback argument very uncertain. We have to rely on models which don't handle clouds well and produce a constant RH.

This is what the models produce a nearly constant RH. So to believe this you have to have faith in the models. This is where the whole AGW and especially

CAGW theory is on shaky ground  scientifically for me. I don't doubt humans are influencing the climate to some degree, I just have my doubts that there

would be "dangerous" interference with the climate system. 

If you would have dug into the site a little further, you'd have seen this:

 

http://www.skepticalscience.com/earth-albedo-effect.htm

 

Ironically, it uses the 1% supposition you just did.

[blizzard1024]

If you would have dug into the site a little further, you'd have seen this:

http://www.skepticalscience.com/earth-albedo-effect.htm

Ironically, it uses the 1% supposition you just did.

That explains the steady temps in this period. Where do they get 3.4 w/m2? That is more than I estimated on my back of envelope calculation.

[f2tornado]

We are putting a significant amount of another greenhouse gas into the atmosphere: water vapor. It doesn't get as much attention as CO2 but the literature is out there to suggest simple H2O from introduced vegetation, swimming pools, reservoirs, and auto exhaust is altering local climate in American Southwest cities like Phoenix and Tuscon. The primary effect is decreasing the diurnal temperature curve with the most notable effect at night as temperatures fail to drop off as fast. The same thing happens in Iowa during peak corn season where 80+ degree dewpoint readings are no longer all that rare. Other land use changes are also most certainly impacting climate on at least local to regional scale. I live in an area where there is a lot of black dirt exposed in fields after harvest and snow melt. This would have been tall grass prairie in 1850. Albedo of black dirt is less than prairie grass. Further in years like this one where no heavy wet snow covered/sealed the soil, blowing dust from exposed fields mixes with snow drastically reducing albedo. Snow on my end of town looks like a DQ Oreo Blizzard right now. I'd like to see more research into impact of land use change on climate. It seems CO2 gets all the buzz since it is the easiest to measure, regulate, and potentially tax. If you're into land use impacts then consider reading some work of Roger Pielke Sr, a respected climatologist and not some fly by night guy on FOX News. He suggests CO2 impact is grossly overstated while other human activity, primarily land use change, is a larger driver of climate change.

[blizzard1024]

We agree where the uncertainties lie. Just to complicate things a bit more, the net feedback from clouds rsults from (albedo + greenhouse effect). The more low cloud the greater scattering to space of surface warming SW radiation from cloud tops. The more low cloud the greater the greenhouse effect. On balance, the net of low cloud is thought to result in negative forcing as the climate warms.

I agree. It probably isn't 2.4 w/m2 as i stated but certainly of the same magnitude of all the man made forcing we have seen. This is reasonable.

[blizzard1024]

We are putting a significant amount of another greenhouse gas into the atmosphere: water vapor. It doesn't get as much attention as CO2 but the literature is out there to suggest simple H2O from introduced vegetation, swimming pools, reservoirs, and auto exhaust is altering local climate in American Southwest cities like Phoenix and Tuscon. The primary effect is decreasing the diurnal temperature curve with the most notable effect at night as temperatures fail to drop off as fast. The same thing happens in Iowa during peak corn season where 80+ degree dewpoint readings are no longer all that rare. Other land use changes are also most certainly impacting climate on at least local to regional scale. I live in an area where there is a lot of black dirt exposed in fields after harvest and snow melt. This would have been tall grass prairie in 1850. Albedo of black dirt is less than prairie grass. Further in years like this one where no heavy wet snow covered/sealed the soil, blowing dust from exposed fields mixes with snow drastically reducing albedo. Snow on my end of town looks like a DQ Oreo Blizzard right now. I'd like to see more research into impact of land use change on climate. It seems CO2 gets all the buzz since it is the easiest to measure, regulate, and potentially tax. If you're into land use impacts then consider reading some work of Roger Pielke Sr, a respected climatologist and not some fly by night guy on FOX News. He suggests CO2 impact is grossly overstated while other human activity, primarily land use change, is a larger driver of climate change.

Although i concur with the potential for land use changes as modifying local climate water vapor from man made sources cycles through the atmosphere so fast it would only have local impact. Not global. Co2 is long lived that is why CO2 is considered forcing and water vapor amounts a feedback.

[blizzard1024]

Pielke Sr. isn't all that trustworthy these days:

http://www.realclimate.org/index.php/archives/2009/07/more-bubkes/langswitch_lang/sp

This assumes real climate is trustworthy. There are many who disagree with this. So what are you objecting to in pielkes work?

[csnavywx]

Except for the part where RealClimate's editors are all climate scientists with a long history of peer-reviewed and vetted research.

[blizzard1024]

Except for the part where RealClimate's editors are all climate scientists with a long history of peer-reviewed and vetted research.

Yes and they all have their whole careers vested in CAGW.

[csnavywx]

Yes and they all have their whole careers vested in CAGW.

CAGW or just climate change in general? I don't see a tilted preference in their research, but maybe that's just me.

 

It's not like this field sprung up overnight. The very same questions you're asking right now were asked 30 years ago. Through relentless observation, testing and research the consensus has been that it's led by primarily by CO2. Virtually every other culprit has been ruled out over that time span in one way or another.

 

As for the climate equilibrium question you posited earlier, we can be reasonably certain that it was in equilibrium via exhaustive temperature reconstructions and parallel paleoclimate data sets. The Holocene has been very tame compared to just about any point previously. Being as the entirety of civilization developed during this calm period and we're in the process of tipping it radically away from that stable state might just be viewed as potentially catastrophic, and I don't think that's an unreasonable supposition.

[f2tornado]

what is the point of asking people to disprove the settled science?

 

Using the term "settled science" is quite condescending loaded language when in reality there is not a whole heck of a lot settled when it comes to anthropgenic climate change beyond C02 being a greenhouse gas. Terms like "prevailing scientific opinion" or "general consensus in the scientific community" are far more appropriate. It would appear RealClimate's beef is Pielke noting trends in the most recent data with RealClimate suggesting Pielke is using too short a time scale. I see merits in both arguments. This certainly doesn't make Pielke untrustworthy.

[blizzard1024]

what is the point of asking people to disprove the settled science?

The atmosphere and climate system are so complex that to think

we humans have it all figured is arrogant on mankind's part.

To equate something as simple as gravity for example as I have

heard "believers" compare to the Earth's complex

atmosphere, oceans, cryosphere, biosphere and land masses

and the interactions is simply wrong. It shows a profound

lack of understanding of how complex this problem really is.  

 

Yours is the exact approach that stifles science and learning.

It is not in the realm of modern science. Reminds of the

time when the church ruled science. Anyone who 

was not in line with the church's ideas was a heretic. 

 

Real climate is to the left as WUWT is to the right in politics. 

Science should never be political.

 

So if you don't like debating your view that the science is

settled then why are you even on this thread? There are

others who want to learn and listen to others viewpoints

with an open mind. 

[blizzard1024]

CAGW or just climate change in general? I don't see a tilted preference in their research, but maybe that's just me.

 

It's not like this field sprung up overnight. The very same questions you're asking right now were asked 30 years ago. Through relentless observation, testing and research the consensus has been that it's led by primarily by CO2. Virtually every other culprit has been ruled out over that time span in one way or another.

 

As for the climate equilibrium question you posited earlier, we can be reasonably certain that it was in equilibrium via exhaustive temperature reconstructions and parallel paleoclimate data sets. The Holocene has been very tame compared to just about any point previously. Being as the entirety of civilization developed during this calm period and we're in the process of tipping it radically away from that stable state might just be viewed as potentially catastrophic, and I don't think that's an unreasonable supposition.

 

The rate change of climate in the Holocene has been roughly plus or minus 2.5C/century from the GISP2

ice core. see graph below. 

 

 

 

This implies significant changes to the climate system in the North Atlantic region which hosts

the North Atlantic Meridional Overturning Current (MOC) which is part of the thermohaline oceanic current that

transports vast amounts of heat to the high latitudes.  This is KEY in the Earth's climate and through the paleorecords

has been shown to have major influence that spreads around the globe through the connected ocean currents.

 

This does show a more stable climate in the holocene but there are still significant

variations in the Holocene related to the MOC. These changes are on the same order of magnitude

of today suggesting our current changing climate is well within the bounds of the natural variations in the

Holocene. This, to me, suggests we can't assume a stable climate in equilibrium in 1850. 

[LakeEffectKing]

Using the term "settled science" is quite condescending loaded language when in reality there is not a whole heck of a lot settled when it comes to anthropgenic climate change beyond C02 being a greenhouse gas. Terms like "prevailing scientific opinion" or "general consensus in the scientific community" are far more appropriate. It would appear RealClimate's beef is Pielke noting trends in the most recent data with RealClimate suggesting Pielke is using too short a time scale. I see merits in both arguments. This certainly doesn't make Pielke untrustworthy.

 

 

The atmosphere and climate system are so complex that to think

we humans have it all figured is arrogant on mankind's part.

To equate something as simple as gravity for example as I have

heard "believers" compare to the Earth's complex

atmosphere, oceans, cryosphere, biosphere and land masses

and the interactions is simply wrong. It shows a profound

lack of understanding of how complex this problem really is.  

 

Yours is the exact approach that stifles science and learning.

It is not in the realm of modern science. Reminds of the

time when the church ruled science. Anyone who 

was not in line with the church's ideas was a heretic. 

 

Real climate is to the left as WUWT is to the right in politics. 

Science should never be political.

 

So if you don't like debating your view that the science is

settled then why are you even on this thread? There are

others who want to learn and listen to others viewpoints

with an open mind. 

Agree very much, but unpopular electric eels self describe themselves in such manner for a reason.  Don't waste your time.  Debate and respond to Don S. and your head will hurt less.

[WeatherRusty]

The atmosphere and climate system are so complex that to think

we humans have it all figured is arrogant on mankind's part.

To equate something as simple as gravity for example as I have

heard "believers" compare to the Earth's complex

atmosphere, oceans, cryosphere, biosphere and land masses

and the interactions is simply wrong. It shows a profound

lack of understanding of how complex this problem really is.  

 

Yours is the exact approach that stifles science and learning.

It is not in the realm of modern science. Reminds of the

time when the church ruled science. Anyone who 

was not in line with the church's ideas was a heretic. 

 

Real climate is to the left as WUWT is to the right in politics. 

Science should never be political.

 

So if you don't like debating your view that the science is

settled then why are you even on this thread? There are

others who want to learn and listen to others viewpoints

with an open mind. 

 

wxtrix demands that information come from within the peer-reviewed scientific literature. That is the only way to eliminate contributions from Tom, Dick and Harry(sorry Harry) or from you for that matter. She is not stiffling anything or anyone, but rather being properly discriminate as to her sources. I don't really care what a skeptic or denier thinks, no matter how plausible their argument. If it does not come from the vetted scientific literature it does not represent science.

[WeatherRusty]

Using the term "settled science" is quite condescending loaded language when in reality there is not a whole heck of a lot settled when it comes to anthropgenic climate change beyond C02 being a greenhouse gas. Terms like "prevailing scientific opinion" or "general consensus in the scientific community" are far more appropriate. It would appear RealClimate's beef is Pielke noting trends in the most recent data with RealClimate suggesting Pielke is using too short a time scale. I see merits in both arguments. This certainly doesn't make Pielke untrustworthy.

 

The science is settled as far as climate scientists are concerned. What science? The Earth is warming and mankind's activities are the reason. No mention of CAGW or any other loaded language.

[SVT450R]

This article just came out in science daily on climate sensitivity.

 

http://www.sciencedaily.com/releases/2013/01/130125103927.htm

 

Global Warming Less Extreme Than Feared? New Estimates from a Norwegian Project On Climate Calculations

Jan. 25, 2013 — Policymakers are attempting to contain global warming at less than 2°C. New estimates from a Norwegian project on climate calculations indicate this target may be more attainable than many experts have feared.  Climate researcher Caroline Leck of Stockholm University has evaluated the Norwegian project and is enthusiastic.

"These results are truly sensational," says Dr Leck. "If confirmed by other studies, this could have far-reaching impacts on efforts to achieve the political targets for climate."

Temperature rise is levelling off

After Earth's mean surface temperature climbed sharply through the 1990s, the increase has levelled off nearly completely at its 2000 level. Ocean warming also appears to have stabilised somewhat, despite the fact that CO₂ emissions and other anthropogenic factors thought to contribute to global warming are still on the rise.

It is the focus on this post-2000 trend that sets the Norwegian researchers' calculations on global warming apart.

Sensitive to greenhouse gases

Climate sensitivity is a measure of how much the global mean temperature is expected to rise if we continue increasing our emissions of greenhouse gases into the atmosphere.

CO₂ is the primary greenhouse gas emitted by human activity. A simple way to measure climate sensitivity is to calculate how much the mean air temperature will rise if we were to double the level of overall CO₂ emissions compared to the world's pre-industrialised level around the year 1750.

If we continue to emit greenhouse gases at our current rate, we risk doubling that atmospheric CO₂ level in roughly 2050.

Mutual influences

A number of factors affect the formation of climate development. The complexity of the climate system is further compounded by a phenomenon known as feedback mechanisms, i.e. how factors such as clouds, evaporation, snow and ice mutually affect one another.

Uncertainties about the overall results of feedback mechanisms make it very difficult to predict just how much of the rise in Earth's mean surface temperature is due to humanmade emissions. According to the Intergovernmental Panel on Climate Change (IPCC) the climate sensitivity to doubled atmospheric CO₂ levels is probably between 2°C and 4.5°C, with the most probable being 3°C of warming.

In the Norwegian project, however, researchers have arrived at an estimate of 1.9°C as the most likely level of warming.

Humanmade climate forcing

"In our project we have worked on finding out the overall effect of all known feedback mechanisms," says project manager Terje Berntsen, who is a professor at the University of Oslo's Department of Geosciences and a senior research fellow at the Center for International Climate and Environmental Research -- Oslo (CICERO). The project has received funding from the Research Council of Norway's Large-scale Programme on Climate Change and its Impacts in Norway (NORKLIMA).

"We used a method that enables us to view the entire earth as one giant 'laboratory' where humankind has been conducting a collective experiment through our emissions of greenhouse gases and particulates, deforestation, and other activities that affect climate."

For their analysis, Professor Berntsen and his colleagues entered all the factors contributing to human-induced climate forcings since 1750 into their model. In addition, they entered fluctuations in climate caused by natural factors such as volcanic eruptions and solar activity. They also entered measurements of temperatures taken in the air, on ground, and in the oceans.

The researchers used a single climate model that repeated calculations millions of times in order to form a basis for statistical analysis. Highly advanced calculations based on Bayesian statistics were carried out by statisticians at the Norwegian Computing Center.

2000 figures make the difference

When the researchers at CICERO and the Norwegian Computing Center applied their model and statistics to analyse temperature readings from the air and ocean for the period ending in 2000, they found that climate sensitivity to a doubling of atmospheric CO₂ concentration will most likely be 3.7°C, which is somewhat higher than the IPCC prognosis.

But the researchers were surprised when they entered temperatures and other data from the decade 2000-2010 into the model; climate sensitivity was greatly reduced to a "mere" 1.9°C.

Professor Berntsen says this temperature increase will first be upon us only after we reach the doubled level of CO₂ concentration (compared to 1750) and maintain that level for an extended time, because the oceans delay the effect by several decades.

Natural changes also a major factor

The figure of 1.9°C as a prediction of global warming from a doubling of atmospheric CO₂ concentration is an average. When researchers instead calculate a probability interval of what will occur, including observations and data up to 2010, they determine with 90% probability that global warming from a doubling of CO₂ concentration would lie between 1.2°C and 2.9°C.

This maximum of 2.9°C global warming is substantially lower than many previous calculations have estimated. Thus, when the researchers factor in the observations of temperature trends from 2000 to 2010, they significantly reduce the probability of our experiencing the most dramatic climate change forecast up to now.

Professor Berntsen explains the changed predictions: "The Earth's mean temperature rose sharply during the 1990s. This may have caused us to overestimate climate sensitivity.

"We are most likely witnessing natural fluctuations in the climate system -- changes that can occur over several decades -- and which are coming on top of a long-term warming. The natural changes resulted in a rapid global temperature rise in the 1990s, whereas the natural variations between 2000 and 2010 may have resulted in the levelling off we are observing now."

Climate issues must be dealt with

Terje Berntsen emphasises that his project's findings must not be construed as an excuse for complacency in addressing human-induced global warming. The results do indicate, however, that it may be more within our reach to achieve global climate targets than previously thought.

Regardless, the fight cannot be won without implementing substantial climate measures within the next few years.

Sulphate particulates

The project's researchers may have shed new light on another factor: the effects of sulphur-containing atmospheric particulates.

Burning coal is the main way that humans continue to add to the vast amounts of tiny sulphate particulates in the atmosphere. These particulates can act as condensation nuclei for cloud formation, cooling the climate indirectly by causing more cloud cover, scientists believe. According to this reasoning, if Europe, the US and potentially China reduce their particulate emissions in the coming years as planned, it should actually contribute to more global warming.

But the findings of the Norwegian project indicate that particulate emissions probably have less of an impact on climate through indirect cooling effects than previously thought.

So the good news is that even if we do manage to cut emissions of sulphate particulates in the coming years, global warming will probably be less extreme than feared.

[blizzard1024]

wxtrix demands that information come from within the peer-reviewed scientific literature. That is the only way to eliminate contributions from Tom, Dick and Harry(sorry Harry) or from you for that matter. She is not stiffling anything or anyone, but rather being properly discriminate as to her sources. I don't really care what a skeptic or denier thinks, no matter how plausible their argument. If it does not come from the vetted scientific literature it does not represent science.

 

Pielke Sr. is a scientist with many publications on land use changes and climate. 

The article I posted is from a source that mostly has peer view literature with

links. I don't disagree with everything in the article just a few points. I hope

others feel this approach is a good way to learn. I am not trying to blast

anyone here. 

[blizzard1024]

huh? the title of this thread is "how do we know CO2 is causing warming?". you admit the settled science is that CO2 is driving global warming but you're reprimanding me for asking why we need to prove the settled science is actually true in a science-based forum?

The title is from skepticalscience and I am NOT questioning that. It is the name of the web article that's all. 

I am not disagreeing with that premise. You misunderstood the whole reason for my posting this. The article

has a lot of good stuff in it which we all agree on. It is the climate sensitivity that I am posing questions

on of which is the uncertain part. You have the wrong idea about me. 

[blizzard1024]

I have already asked you ONCE to stop misrepresenting what I post. I am now asking you a second time to cease this disruptive behavior.

what is the value of non-factual information posted in a science-based forum? why can't anyone on the denier side answer that question?

we're well aware you don't think CO2 is an issue. that opinion isn't verified by the science and your continual insertion of this false assertion into the debates here serves only to disrupt the science-based discussion people are trying to have.

if you have peer-reviewed science that disproves the contentions in the entry from skepticalscience that you linked to in the first post, I invite you to post it with all haste.

 

Well when you post stuff like you do, you deserve responses like this. I am asking you to quit being so close-minded and arrogant

on this forum. If you don't like a thread...stay off it. Its your choice. 

[Jonger]

We are putting a significant amount of another greenhouse gas into the atmosphere: water vapor. It doesn't get as much attention as CO2 but the literature is out there to suggest simple H2O from introduced vegetation, swimming pools, reservoirs, and auto exhaust is altering local climate in American Southwest cities like Phoenix and Tuscon. The primary effect is decreasing the diurnal temperature curve with the most notable effect at night as temperatures fail to drop off as fast. The same thing happens in Iowa during peak corn season where 80+ degree dewpoint readings are no longer all that rare. Other land use changes are also most certainly impacting climate on at least local to regional scale. I live in an area where there is a lot of black dirt exposed in fields after harvest and snow melt. This would have been tall grass prairie in 1850. Albedo of black dirt is less than prairie grass. Further in years like this one where no heavy wet snow covered/sealed the soil, blowing dust from exposed fields mixes with snow drastically reducing albedo. Snow on my end of town looks like a DQ Oreo Blizzard right now. I'd like to see more research into impact of land use change on climate. It seems CO2 gets all the buzz since it is the easiest to measure, regulate, and potentially tax. If you're into land use impacts then consider reading some work of Roger Pielke Sr, a respected climatologist and not some fly by night guy on FOX News. He suggests CO2 impact is grossly overstated while other human activity, primarily land use change, is a larger driver of climate change.

 

Land-form changes are probably a significant part of AGW... How can all that concrete and tree removable not result in a substantial percent change in global temps?

[Snow_Miser]

This article just came out in science daily on climate sensitivity.

 

http://www.sciencedaily.com/releases/2013/01/130125103927.htm

 

Global Warming Less Extreme Than Feared? New Estimates from a Norwegian Project On Climate Calculations

Jan. 25, 2013 — Policymakers are attempting to contain global warming at less than 2°C. New estimates from a Norwegian project on climate calculations indicate this target may be more attainable than many experts have feared.  Climate researcher Caroline Leck of Stockholm University has evaluated the Norwegian project and is enthusiastic.

"These results are truly sensational," says Dr Leck. "If confirmed by other studies, this could have far-reaching impacts on efforts to achieve the political targets for climate."

Temperature rise is levelling off

After Earth's mean surface temperature climbed sharply through the 1990s, the increase has levelled off nearly completely at its 2000 level. Ocean warming also appears to have stabilised somewhat, despite the fact that CO₂ emissions and other anthropogenic factors thought to contribute to global warming are still on the rise.

It is the focus on this post-2000 trend that sets the Norwegian researchers' calculations on global warming apart.

Sensitive to greenhouse gases

Climate sensitivity is a measure of how much the global mean temperature is expected to rise if we continue increasing our emissions of greenhouse gases into the atmosphere.

CO₂ is the primary greenhouse gas emitted by human activity. A simple way to measure climate sensitivity is to calculate how much the mean air temperature will rise if we were to double the level of overall CO₂ emissions compared to the world's pre-industrialised level around the year 1750.

If we continue to emit greenhouse gases at our current rate, we risk doubling that atmospheric CO₂ level in roughly 2050.

Mutual influences

A number of factors affect the formation of climate development. The complexity of the climate system is further compounded by a phenomenon known as feedback mechanisms, i.e. how factors such as clouds, evaporation, snow and ice mutually affect one another.

Uncertainties about the overall results of feedback mechanisms make it very difficult to predict just how much of the rise in Earth's mean surface temperature is due to humanmade emissions. According to the Intergovernmental Panel on Climate Change (IPCC) the climate sensitivity to doubled atmospheric CO₂ levels is probably between 2°C and 4.5°C, with the most probable being 3°C of warming.

In the Norwegian project, however, researchers have arrived at an estimate of 1.9°C as the most likely level of warming.

Humanmade climate forcing

"In our project we have worked on finding out the overall effect of all known feedback mechanisms," says project manager Terje Berntsen, who is a professor at the University of Oslo's Department of Geosciences and a senior research fellow at the Center for International Climate and Environmental Research -- Oslo (CICERO). The project has received funding from the Research Council of Norway's Large-scale Programme on Climate Change and its Impacts in Norway (NORKLIMA).

"We used a method that enables us to view the entire earth as one giant 'laboratory' where humankind has been conducting a collective experiment through our emissions of greenhouse gases and particulates, deforestation, and other activities that affect climate."

For their analysis, Professor Berntsen and his colleagues entered all the factors contributing to human-induced climate forcings since 1750 into their model. In addition, they entered fluctuations in climate caused by natural factors such as volcanic eruptions and solar activity. They also entered measurements of temperatures taken in the air, on ground, and in the oceans.

The researchers used a single climate model that repeated calculations millions of times in order to form a basis for statistical analysis. Highly advanced calculations based on Bayesian statistics were carried out by statisticians at the Norwegian Computing Center.

2000 figures make the difference

When the researchers at CICERO and the Norwegian Computing Center applied their model and statistics to analyse temperature readings from the air and ocean for the period ending in 2000, they found that climate sensitivity to a doubling of atmospheric CO₂ concentration will most likely be 3.7°C, which is somewhat higher than the IPCC prognosis.

But the researchers were surprised when they entered temperatures and other data from the decade 2000-2010 into the model; climate sensitivity was greatly reduced to a "mere" 1.9°C.

Professor Berntsen says this temperature increase will first be upon us only after we reach the doubled level of CO₂ concentration (compared to 1750) and maintain that level for an extended time, because the oceans delay the effect by several decades.

Natural changes also a major factor

The figure of 1.9°C as a prediction of global warming from a doubling of atmospheric CO₂ concentration is an average. When researchers instead calculate a probability interval of what will occur, including observations and data up to 2010, they determine with 90% probability that global warming from a doubling of CO₂ concentration would lie between 1.2°C and 2.9°C.

This maximum of 2.9°C global warming is substantially lower than many previous calculations have estimated. Thus, when the researchers factor in the observations of temperature trends from 2000 to 2010, they significantly reduce the probability of our experiencing the most dramatic climate change forecast up to now.

Professor Berntsen explains the changed predictions: "The Earth's mean temperature rose sharply during the 1990s. This may have caused us to overestimate climate sensitivity.

"We are most likely witnessing natural fluctuations in the climate system -- changes that can occur over several decades -- and which are coming on top of a long-term warming. The natural changes resulted in a rapid global temperature rise in the 1990s, whereas the natural variations between 2000 and 2010 may have resulted in the levelling off we are observing now."

Climate issues must be dealt with

Terje Berntsen emphasises that his project's findings must not be construed as an excuse for complacency in addressing human-induced global warming. The results do indicate, however, that it may be more within our reach to achieve global climate targets than previously thought.

Regardless, the fight cannot be won without implementing substantial climate measures within the next few years.

Sulphate particulates

The project's researchers may have shed new light on another factor: the effects of sulphur-containing atmospheric particulates.

Burning coal is the main way that humans continue to add to the vast amounts of tiny sulphate particulates in the atmosphere. These particulates can act as condensation nuclei for cloud formation, cooling the climate indirectly by causing more cloud cover, scientists believe. According to this reasoning, if Europe, the US and potentially China reduce their particulate emissions in the coming years as planned, it should actually contribute to more global warming.

But the findings of the Norwegian project indicate that particulate emissions probably have less of an impact on climate through indirect cooling effects than previously thought.

So the good news is that even if we do manage to cut emissions of sulphate particulates in the coming years, global warming will probably be less extreme than feared.

 

An equilibrium sensitivity of 1.9 Degrees C, which was the most likely value found in the study, would be the sensitivity in the GCMs without any Cloud Feedback.

[Snow_Miser]

It is quite certain that solar radiative forcing (TSI) has been very small relative to the anthropogenic forcing since the Maunder Minimum (0.12W/m^2 vrs. 1.6W/m^2). The only other variable which matters is albedo, and since clouds act as feedback to warming and under the presumption of near constant RH, cloudiness shouldn't change that much. Otherwise a small change in low cloud amount due to warming would act as a slight negative feedback, while never being able to negate the original external forcing.

 

That depends on if there has been any change in the Cloud Cover associated with Solar Activity, and other such amplification mechanisms.

[skierinvermont]

That depends on if there has been any change in the Cloud Cover associated with Solar Activity, and other such amplification mechanisms.

 

 

Well where is the dramatic change in cloud cover and temperature over the course of the solar cycle, especially in the case of the exceptionally deep prolonged recent minimum?

[skierinvermont]

Land-form changes are probably a significant part of AGW... How can all that concrete and tree removable not result in a substantial percent change in global temps?

 

Deforestation is actually a significant factor globally. It causes cooling because deforested areas have a higher albedo. 

 

 

Concrete, while it seems significant is such a microscopic % of the earth I haven't heard of it being considered a significant factor. Your perception of how much concrete there is is probably altered by constantly being in populated areas.