The Basics: What is Global Warming and What is the Greenhouse Effect?

[Grat3fulh3ad]

Me too, I'd like them to be right. But I tend to lean on the science.

beats the hell outta unsubstantiated wishful assumption or regurgitated polititroll rhetoric for figuring stuff out...

 

[SpasticGramps]

I reckon most who post in this thread understand how I feel about the environment. If not I'll sum it up real quick. Humans are nasty polluters who exploit mother Earth and offer little in return aside from decomposing bodies that make good compost in the end. Kind of like every other animal I guess. BTW I've spent a lot of money on my house to make it as green as possible. Substantial energy dependence is also necessary for our continued survival as a species.

Having said that, what we are arguing is two irreconcilable paradigms. Whether you like it or not it's psychologically the same thing as arguing religion. In the majority camp there are the believers, in the minority there are the "deniers." I suppose you could throw in the agnostics as a third paradigm. One side has the consensus of the scientific community, the other mainly distrust of the establishment as a whole.

One camp sees this a a purely scientific issue. The others see it as a political issue and cannot speak of it without bringing that argument to bear. Given the rules of the board it's easy to see which paradigm will prevail here.

So, I say to my fellow "deniers," my fellow blasphemers, and my fellow Galileon heretics, grab your crosses, nails, and hammers, and lets head to the knoll on Golgatha. Dare not to speak your mind for fear of banishment from the garden of Eden for only one paradigm is allowed to be discussed here.

In the end, all we are arguing is illusions of reality.

"I know that I know nothing" Socrates



I'll stop waxing poetically and leave y'all to continue with your one sided paradigm. My evidence sucks anyway.

 

[Nor'Easter]

I am sorry you feel that way SG, I thought you were starting to make sense! The truth is nowhere near as black and white as you say, both sides are not perfect. However, it is the denier side that tends to treat this issue as a political or religious one, calling people names or calling people closed-minded when they are the very essence of that which they supposedly oppose. Religion tends so stress faith, with no evidence or proof and stresses that you are to have faith without proof. The people in the AGW camp are people whose beliefs are backed up by real hard science. They have faith in their position, but not because some higher power brands them a sinner if they don't, but because they did a lot of painstaking research over decades, and the facts back them up! Whereas the denier camp as you called it, stresses faith in the individual (your God is ME and all that matters is ME) and the individuals desires/wants/needs over the good of humanity as a whole. If anyone wants to control selfishness or greed, they are called leftists and worse. If anyone wants to do anything about the problem, they are out to take away everyone's freedom. But in any civilized society, there are limits to personal freedom when the greater good is disproportionately harmed. Should you be allowed to dump toxic waste in the river out back just because it impinges on your freedom to be lazy and not dispose of it properly? So you have it all backwards and I am profoundly disappoint in you man. I thought you were opening your mind to other possibilities and now I see I was wrong.

 

[Nor'Easter]

I agree Head, we should all start ignoring the trolls, don't feed the animals, that kind of thing. Those that come here only to refute without proof should not be responded to.

 

[maryj315]

I agree Head, we should all start ignoring the trolls, don't feed the animals, that kind of thing. Those that come here only to refute without proof should not be responded to.

I concur with you Nor, however that is not going to transpire. The majority of the skeptics that frequent this forum recognize AGW as just another instrument or weapon used to exploit their freedom. This is war to them actualities and morality do not apply when you are fighting to preserve your freedoms. They view all our scientific data as indoctrination while viewing us as useful idiots. One can only hope they will tolerate ignoring them.

Mj

 

[slave4sail]

To be clear I do not have a side on this topic, however to be fair for both sides of this argument view with an open mind and heart as much I am able to. After an argument is what it really is, after the beliefs are pushed aside; it is an ego fest on both sides.

I would like to point out that science is not fact. If it were the earth would still be flat, so before these science and figures are to be held as truth; I would like to have a better understanding of physics and the world around us. As I see it now, we are unable to comprehend these mechanics; and this is the reason so many of our theories in science do not hold up when taken to extreme calculations.

Science to me is just a way we explain what we see, so for everyone this will be different. Cumulatively we can use these explanations and it may help us understand something, however as noted above our understanding of the world around us is so limited; and mostly blocked by our human ego.

I appreciate all of those who have contributed to this discussion, but let us remember for many years all the science pointed towards the earth being flat. Then again, it may be! Like I said, I do not have a side on this topic; and believe that anything and everything that ever happens is natural. Our individual and cumulative experience on earth right now is a precious gift, so enjoy the experience. Please do not let the science or religion, or the words we use to express our understanding for the world around us sidestep that fact. Both sides have the same amount of credibility in my opinion, so before we judge others opinions let us remember we like specimens in a seed variety are exposed to our own unique selective pressures in life. Interesting topic. Always enjoy reading your comments spastic.g. nam myoho renge kyo

 

[WeSeekTheTruth]

I have to start by saying that this article is absolute proof that cavemen have caused modern global warming.

But, sometimes I wonder if we argue that deforestation is a main cause of global warming, then we argue that forests are the cause of global warming......seems to be a no win situation.

Since politics is a big no-no for J-J, now that I have completely decimated the opposing ranks, I will now show the hypocrisy of our scientific establishment.

I will do this with little or no political rhetoric.

Human-Made Global Warming Started With Ancient Hunters

ScienceDaily (July 1, 2010) — Even before the dawn of agriculture, people may have caused the planet to warm up, a new study suggests.

Mammoths used to roam modern-day Russia and North America, but are now extinct -- and there's evidence that around 15,000 years ago, early hunters had a hand in wiping them out. A new study, accepted for publication in Geophysical Research Letters, a journal of the American Geophysical Union (AGU), argues that this die-off had the side effect of heating up the planet.

"A lot of people still think that people are unable to affect the climate even now, even when there are more than 6 billion people," says the lead author of the study, Chris Doughty of the Carnegie Institution for Science in Stanford, California. The new results, however, "show that even when we had populations orders of magnitude smaller than we do now, we still had a big impact."

In the new study, Doughty, Adam Wolf, and Chris Field -- all at Carnegie Institution for Science -- propose a scenario to explain how hunters could have triggered global warming.

First, mammoth populations began to drop -- both because of natural climate change as the planet emerged from the last ice age, and because of human hunting. Normally, mammoths would have grazed down any birch that grew, so the area stayed a grassland. But if the mammoths vanished, the birch could spread. In the cold of the far north, these trees would be dwarfs, only about 2 meters (6 feet) tall. Nonetheless, they would dominate the grasses.

The trees would change the color of the landscape, making it much darker so it would absorb more of the Sun's heat, in turn heating up the air. This process would have added to natural climate change, making it harder for mammoths to cope, and helping the birch spread further.

To test how big of an effect this would have on climate, Field's team looked at ancient records of pollen, preserved in lake sediments from Alaska, Siberia, and the Yukon Territory, built up over thousands of years. They looked at pollen from birch trees (the genus Betula), since this is "a pioneer species that can rapidly colonize open ground following disturbance," the study says. The researchers found that around 15,000 years ago -- the same time that mammoth populations dropped, and that hunters arrived in the area -- the amount of birch pollen started to rise quickly.

To estimate how much additional area the birch might have covered, they started with the way modern-day elephants affect their environment by eating plants and uprooting trees. If mammoths had effects on vegetation similar to those of modern elephants , then the fall of mammoths would have allowed birch trees to spread over several centuries, expanding from very few trees to covering about one-quarter of Siberia and Beringia -- the land bridge between Asia and Alaska. In those places where there was dense vegetation to start with and where mammoths had lived, the main reason for the spread of birch trees was the demise of mammoths, the model suggests.

Another study, published last year, shows that "the mammoths went extinct, and that was followed by a drastic change in the vegetation," rather than the other way around, Doughty says. "With the extinction of this keystone species, it would have some impact on the ecology and vegetation -- and vegetation has a large impact on climate."

Doughty and colleagues then used a climate simulation to estimate that this spread of birch trees would have warmed the whole planet more than 0.1 degrees Celsius (0.18 degrees Fahrenheit) over the course of several centuries. (In comparison, the planet has warmed about six times more during the past 150 years, largely because of people's greenhouse gas emissions.)

Only some portion -- about one-quarter -- of the spread of the birch trees would have been due to the mammoth extinctions, the researchers estimate. Natural climate change would have been responsible for the rest of the expansion of birch trees. Nonetheless, this suggests that when hunters helped finish off the mammoth, they could have caused some global warming.

In Siberia, Doughty says, "about 0.2 degrees C (0.36 degrees F) of regional warming is the part that is likely due to humans."

Earlier research indicated that prehistoric farmers changed the climate by slashing and burning forests starting about 8,000 years ago, and when they introduced rice paddy farming about 5,000 years ago. This would suggest that the start of the so-called "Anthropocene" -- a term used by some scientists to refer to the geological age when human beings began shaping the entire planet -- should be dated to several thousand years ago.

However, Field and colleagues argue, the evidence of an even earlier human-made global climate impact suggests the Anthropocene could have started much earlier. Their results, they write, "suggest the human influence on climate began even earlier than previously believed, and that the onset of the Anthropocene should be extended back many thousands of years."

This work was funded by the Carnegie Institution for Science and NASA.

 

[Grat3fulh3ad]

science NEVER pointed toward a flat earth...

 

[Grat3fulh3ad]

funny, weseek...
The article says it started back then, so you imply it said "it all happened back then"

typical of the propaganda rhetoric that needs ignoring.

 

[Grat3fulh3ad]

I have to start by saying that this article is absolute proof that cavemen have caused modern global warming.

"Human-Made Global Warming Started With Ancient Hunters"

absolute proof that cavemen caused???

you have reality issues... maybe the delusions you suffer from are treatable?

 

[Grat3fulh3ad]

that is a good article, though, Amos... It well demonstrates the effect mankind has always had on our environment...

Doughty and colleagues then used a climate simulation to estimate that this spread of birch trees would have warmed the whole planet more than 0.1 degrees Celsius (0.18 degrees Fahrenheit) over the course of several centuries. (In comparison, the planet has warmed about six times more during the past 150 years, largely because of people's greenhouse gas emissions.)

 

[WeSeekTheTruth]

"Human-Made Global Warming Started With Ancient Hunters"

absolute proof that cavemen caused???

you have reality issues... maybe the delusions you suffer from are treatable?

That's enough now, H3ad, I'm going to tell JJ you're picking on me again.

 

[Grat3fulh3ad]

Whenever controversies arise that pit scientists against segments of the U.S. public -- the evolution debate, say, or the fight over vaccination -- a predictable dance seems to unfold. One the one hand, the nonscientists appear almost entirely impervious to scientific data that undermine their opinions and prone to arguing back with technical claims that are of dubious merit. In response, the scientists shake their heads and lament that if only the public weren't so ignorant, these kinds of misunderstandings wouldn't occur.

But what if the fault actually lies with both sides?

We've been aware for a long time that Americans don't know much about science. Surveys that measure the public's views on evolution, climate change, the big bang and even the idea that the Earth revolves around the sun yield a huge gap between what science tells us and what the public believes.

But that's not the whole story. The American Academy of Arts and Sciences convened a series of workshops on this topic over the past year and a half, and many of the scientists and other experts who participated concluded that, as much as the public misunderstands science, scientists misunderstand the public. In particular, they often fail to realize that a more scientifically informed public is not necessarily a public that will more frequently side with scientists.

Take climate change. The battle over global warming has raged for more than a decade, with experts still stunned by the willingness of their political opponents to distort scientific conclusions. They conclude, not illogically, that they're dealing with a problem of misinformation or downright ignorance -- one that can be fixed only by setting the record straight

Yet a closer look complicates that picture. For one thing, it's political outlook -- not education -- that seems to motivate one's belief on this subject. According to polling performed by the Pew Research Center, Republicans who are college graduates are considerably less likely to accept the scientific consensus on climate change than those who have less education. These better-educated Republicans probably aren't ignorant; a more likely explanation is that they are politically driven consumers of climate science information. Among Democrats and independents, the relationship between education and beliefs about global warming is precisely the opposite -- more education leads to greater acceptance of the consensus climate science.

In other words, it appears that politics comes first on such a contested subject, and better information is no cure-all -- people are likely to simply strain it through an ideological sieve. In fact, more education probably makes a global warming skeptic more persuasive, and more adept at collecting information and generating arguments sympathetic to his or her point of view.

A similar story unfolds with public opposition to vaccination. Once again, on a technical level, skeptics get the science wrong. The body of epidemiological evidence overwhelmingly shows that vaccines don't cause autism. Furthermore, the principal agent accused of having this effect (a mercury-based preservative called thimerosal) has long since been removed from most childhood vaccines. Yet autism rates have not declined.

With public health at stake, it's no wonder medical experts get frustrated when they hear autism activists such as actress Jenny McCarthy attack vaccines. But once again, the skeptics aren't simply ignorant people. If anything, they seem to be more voracious consumers of the relevant medical information than the nation as a whole. According to a 2009 study in the New England Journal of Medicine, children who go unvaccinated by parental choice (rather than because of inadequate access to vaccines) tend to be white, from well-to-do families and with married, college-educated mothers. Parents in such families are more likely to go onto the Internet (what McCarthy calls the "university of Google") to research the health risks of inoculation than are other groups of parents.

Or consider the long-running controversy over plans to dispose of the nation's nuclear waste at Nevada's Yucca Mountain. Although many technical experts have long argued that the repository would be safe, this has hardly convinced frightened and angry Nevadans. In 1991, the American Nuclear Energy Council even launched an ad campaign to educate the public about the Yucca Mountain plan but it backfired. Nearly a third of viewers became more resistant to the repository, and among those who were already opposed, their resolve strengthened. (Just 15 percent had a more favorable opinion of the repository after seeing the ad, and half of viewers did not change their minds.)

These three controversies have a single moral, and it's that experts who want Americans to take science into account when they form opinions on contentious issues need to do far more than just "lay out the facts" or "set the record straight." What science says is important, but in controversial areas, it's only the beginning. It's critical that experts and policy makers better understand what motivates public concern in the first place; and in this, they mustn't be deceived by the fact that people often appear, on the surface, to be arguing about scientific facts. Frequently, their underlying rationale is very different.

Thus, for instance, resistance to climate science in the United States seems to be linked to a libertarian economic outlook: People who resist what experts tell them about global warming often appear, at heart, to be most worried about the consequences of increased government regulation of carbon emissions. Similarly, based upon my observation, vaccine skepticism seems closely connected to distrust of the pharmaceutical industry and of the federal government's medical research establishment. As for Yucca Mountain, much of the outrage appears to originate in the perceived unfairness of having Nevada proposed as the sole dump site for the waste of an entire nation.

For this reason, initiatives that engage the public about science policy in a two-way conversation -- before controversies explode -- show great promise. In Canada, for instance, the national Nuclear Waste Management Organization spent three years listening to the public's views about how to handle nuclear waste disposal and promised that no dump or repository would be sprung on a community without its consent. Throughout the process, even critics of waste storage efforts remained engaged and supportive of attempts to come up with the best possible solution. In the United States, meanwhile, the federally funded National Nanotechnology Initiative has sponsored a great deal of social science research to explore possible public concerns that may arise as this new field of technology advances.

Experts aren't wrong in thinking that Americans don't know much about science, but given how little they themselves often know about the public, they should be careful not to throw stones. Rather than simply crusading against ignorance, the defenders of science should also work closely with social scientists and specialists in public opinion to determine how to defuse controversies by addressing their fundamental causes.

They might, in the process, find a few pleasant surprises. For one thing, the public doesn't seem to disdain scientists, as scientists often suppose. A 2009 study by the Pew Research Center for the People & the Press found that Americans tend to have positive views of the scientific community; it's scientists who are wary of the media and the public.

 

[Grat3fulh3ad]

That's enough now, H3ad, I'm going to tell JJ you're picking on me again.

I only pick on your distortion and spin.


it seems to be quite the humongous stretch of imagination to imply that that article provided absolute proof of cavemen causing modern global warming.....

Especially since the article neither says nor implies any such thing even remotely.


why don't you abandon the political tactics and try simply being honest with yourself and us?

 

[slave4sail]

science NEVER pointed toward a flat earth...

We shall continue to consider our sources as we see fit. How exactly does the concept of time work with the role it plays in science? Now to use this time measurement as an accurate gauge to things we already have a limited scope of.

I am saying our experiences have not changed, only the terminology. I agree it makes scientific sense with much of what you say head, especially on this topic. However I will not let that sway me into believing these things which make great sense when applied to science just as I will not let biblical things sway me when applied to the bible.

Consider your sources, and value the experience. What does it matter, we can only control our own actions. All it takes is groundbreaking new scientific evidence of something to change everything as we (scientifically) know it, a total mind blower! Like when they went from the cumulative gathered scientific data at the time to go from the assumption the earth was flat to being round. Yes the science used to point that way. You can believe what you want, as we all will. Belief in your facts are the same belief in mine, the same as everyone else. We are not so different, only humans sharing an experience. I believe in just enjoying the experience, again great topic. Great use of insight from other points of view, and it is valued.

 

[Grat3fulh3ad]

Please post up something to support your false assertion that the scientific method ever led to a flat earth theory...

methinks you are confusing myth and history.

 

[WeSeekTheTruth]

Some people appear to imply that by using the word "science" they can influence more people who are not smart enough to know better.

 

[Grat3fulh3ad]

A History of Climate Change Science

"To a patient scientist, the unfolding greenhouse mystery is far more exciting than the plot of the best mystery novel. But it is slow reading, with new clues sometimes not appearing for several years. Impatience increases when one realizes that it is not the fate of some fictional character, but of our planet and species, which hangs in the balance as the great carbon mystery unfolds at a seemingly glacial pace."
— D. Schindler(1)

It is an epic story: the struggle of thousands of men and women over the course of a century for very high stakes. For some, the work required actual physical courage, a risk to life and limb in icy wastes or on the high seas. The rest needed more subtle forms of courage. They gambled decades of arduous effort on the chance of a useful discovery, and staked their reputations on what they claimed to have found. Even as they stretched their minds to the limit on intellectual problems that often proved insoluble, their attention was diverted into grueling administrative struggles to win minimal support for the great work. A few took the battle into the public arena, often getting more blame than praise; most labored to the end of their lives in obscurity. In the end they did win their goal, which was simply knowledge.

The scientists who labored to understand the Earth's climate discovered that many factors influence it. Everything from volcanoes to factories shape our winds and rains. The scientific research itself was shaped by many influences, from popular misconceptions to government funding, all happening at once. A traditional history would try to squeeze the story into a linear text, one event following another like beads on a string. Inevitably some parts are left out. Yet for this sort of subject we need total history, including all the players — mathematicians and biologists, lab technicians and government bureaucrats, industrialists and politicians, newspaper reporters and the ordinary citizen. This Web site is an experiment in a new way to tell a historical story. Think of the site as an object like a sculpture or a building. You walk around, looking from this angle and that. In your head you are putting together a rounded representation, even if you don't take the time to inspect every cranny. That is the way we usually learn about anything complex.


The story in a nutshell: People have long suspected that human activity could change the local climate. For example, ancient Greeks and 19th-century Americans debated how cutting down forests might bring more rainfall to a region, or perhaps less. But there were larger shifts of climate that happened all by themselves. The discovery of ice ages in the distant past proved that climate could change radically over the entire globe, which seemed vastly beyond anything mere humans could provoke. Then what did cause global climate change — was it variations in the heat of the Sun? Volcanoes erupting clouds of smoke? The raising and lowering of mountain ranges, which diverted wind patterns and ocean currents? Or could it be changes in the composition of the air itself?

In 1896 a Swedish scientist published a new idea. As humanity burned fossil fuels such as coal, which added carbon dioxide gas to the Earth's atmosphere, we would raise the planet's average temperature. This "greenhouse effect" was only one of many speculations about climate change, however, and not the most plausible. Scientists found technical reasons to argue that our emissions could not change the climate. Indeed most thought it was obvious that puny humanity could never affect the vast climate cycles, which were governed by a benign "balance of nature." In any case major change seemed impossible except over tens of thousands of years.

In the 1930s, people realized that the United States and North Atlantic region had warmed significantly during the previous half-century. Scientists supposed this was just a phase of some mild natural cycle, with unknown causes. Only one lone voice, the amateur G.S. Callendar, insisted that greenhouse warming was on the way. Whatever the cause of warming, everyone thought that if it happened to continue for the next few centuries, so much the better.

In the 1950s, Callendar's claims provoked a few scientists to look into the question with improved techniques and calculations. What made that possible was a sharp increase of government funding, especially from military agencies with Cold War concerns about the weather and the seas. The new studies showed that, contrary to earlier crude estimates, carbon dioxide could indeed build up in the atmosphere and should bring warming. Painstaking measurements drove home the point in 1960 by showing that the level of the gas was in fact rising, year by year.

Over the next decade a few scientists devised simple mathematical models of the climate, and turned up feedbacks that could make the system surprisingly variable. Others figured out ingenious ways to retrieve past temperatures by studying ancient pollens and fossil shells. It appeared that grave climate change could happen, and in the past had happened, within as little as a few centuries. This finding was reinforced by computer models of the general circulation of the atmosphere, the fruit of a long effort to learn how to predict (and perhaps even deliberately change) the weather. Calculations made in the late 1960s suggested that average temperatures would rise a few degrees within the next century. But the next century seemed far off, and the models were preliminary. Groups of scientists that reviewed the calculations found them plausible but saw no need for any policy action, aside from putting more effort into research to find out for sure what was happening.

In the early 1970s, the rise of environmentalism raised public doubts about the benefits of human activity for the planet. Curiosity about climate turned into anxious concern. Alongside the greenhouse effect, some scientists pointed out that human activity was putting dust and smog particles into the atmosphere, where they could block sunlight and cool the world. Moreover, analysis of Northern Hemisphere weather statistics showed that a cooling trend had begun in the 1940s. The mass media (to the limited extent they covered the issue) were confused, sometimes predicting a balmy globe with coastal areas flooded as the ice caps melted, sometimes warning of the prospect of a catastrophic new ice age. Study panels, first in the U.S. and then elsewhere, began to warn that one or another kind of future climate change might pose a severe threat. The only thing most scientists agreed on was that they scarcely understood the climate system, and much more research was needed. Research activity did accelerate, including huge data-gathering schemes that mobilized international fleets of oceanographic ships and orbiting satellites.

Earlier scientists had sought a single master-key to climate, but now they were coming to understand that climate is an intricate system responding to a great many influences. Volcanic eruptions and solar variations were still plausible causes of change, and some argued these would swamp any effects of human activities. Even subtle changes in the Earth's orbit could make a difference. To the surprise of many, studies of ancient climates showed that astronomical cycles had partly set the timing of the ice ages. Apparently the climate was so delicately balanced that almost any small perturbation might set off a great shift. According to the new "chaos" theories, in such a system a shift might even come all by itself — and suddenly. Support for the idea came from ice cores arduously drilled from the Greenland ice sheet. They showed large and disconcertingly abrupt temperature jumps in the past.

Greatly improved computer models began to suggest how such jumps could happen, for example through a change in the circulation of ocean currents. Experts predicted droughts, storms, rising sea levels, and other disasters. A few politicians began to suspect there might be a public issue here. However, the modelers had to make many arbitrary assumptions about clouds and the like, and reputable scientists disputed the reliability of the results. Others pointed out how little was known about the way living ecosystems interact with climate and the atmosphere. They argued, for example, over the effects of agriculture and deforestation in adding or subtracting carbon dioxide from the air. One thing the scientists agreed on was the need for a more coherent research program. But the research remained disorganized, and funding grew only in irregular surges. The effort was dispersed among many different scientific fields, each with something different to say about climate change.

One unexpected discovery was that the level of certain other gases was rising, which would add seriously to global warming. Some of these gases also degraded the atmosphere's protective ozone layer, and the news inflamed public worries about the fragility of the atmosphere. Moreover, by the late 1970s global temperatures had begun to rise again. Many climate scientists had become convinced that the rise was likely to continue as greenhouse gases accumulated. By around 2000, some predicted, an unprecedented global warming would become apparent. Their worries first caught wide public attention in the summer of 1988, the hottest on record till then. (Most since then have been hotter.) An international meeting of scientists warned that the world should take active steps to cut greenhouse gas emissions.

The response was vehement. Corporations and individuals who opposed all government regulation began to spend many millions of dollars on lobbying, advertising, and "reports" that mimicked scientific publications, in an effort to convince people that there was no problem at all. Environmental groups, less wealthy but more enthusiastic, helped politicize the issue with urgent cries of alarm. But the many scientific uncertainties, and the sheer complexity of climate, made room for limitless debate over what actions, if any, governments should take.

Here's what all scientists agreed they knew by 1988

To stay at a constant temperature, the Earth must radiate as much energy as it receives from the Sun. We receive this energy mostly as visible light which warms the surface. Being much cooler than the Sun, the Earth radiates most of its energy as infrared rays. A calculation using basic laws of physics shows that a planet at our distance from the Sun, emitting the same total amount of energy as it receives, will have a temperature well below freezing. Then why is the actual average surface temperature higher, about 14°C? Infrared radiation beaming up from the surface is intercepted by "greenouse" gas molecules in the lower atmosphere, and that keeps the lower atmosphere and the surface warm. The radiation that finally escapes is mostly emitted from higher levels of the atmosphere, levels that are indeed well below freezing (-18°C, for details see the essay on simple models).

The nitrogen and oxygen gases that make up most of the atmosphere don't intercept infrared radiation. The most important greenhouse gases are water vapor and carbon dioxide (CO2). The level of carbon dioxide in the atmosphere was observed to be rising rapidly, and the only reasonable explanation was that this was due to the enormous emissions from human activities.

A rather straightforward calculation showed that doubling the level of carbon dioxide in the atmosphere... which would arrive in the late 21st century if no steps were taken to curb emissions... should raise the temperature of the surface roughly one degree C. However, a warmer atmosphere would hold more water vapor, which ought to cause another degree or so of warming. Beyond that the calculations got problematic. Cloudiness was likely to change in ways that could either enhance or diminish the warming, and scientists did not understand the complex processes well. Moreover, humanity was emitting ever increasing amounts of smoke and other pollution; again scientists were not sure how this might affect climate. Only better observations and computer models could attempt to project the outcome.

Scientists intensified their research, organizing programs on an international scale. Was the global temperature rise due to an increase in the Sun’s activity? Solar activity began to decline, but the temperature soared faster than ever. Did computer models reproduce the present climate only because they were tweaked until they matched it, making them worthless for calculating a future climate change? Improved models successfully predicted the temporary cooling due to a huge volcanic explosion in 1991 and passed many other tests. In particular, the modelers could now reproduce in detail the pattern of warming, changes in rainfall, etc. actually observed in different regions of the world over the past century. Nobody had been able to build a model that matched the historical record and that did not show significant warming when greenhouse gases were added.

The physics of clouds and pollution remained too complex to work out exactly, and modeling teams that made different assumptions got somewhat different results. Most of them found a warming of around 3°C when the carbon dioxide level doubled, late in the 21st century. But some found a rise of 2°C or perhaps a bit less, a costly but manageable warming. Others calculated a 5°C rise or even more, an unparalleled catastrophe.

Meanwhile striking news came from studies of ancient climates recorded in Antarctic ice cores. For hundreds of thousands of years, carbon dioxide and temperature had been linked: anything that caused one of the pair to rise or fall had caused a rise or fall in the other. It turned out that a doubling of carbon dioxide had always gone along with a 3°C temperature rise, give or take a degree or two — a striking confirmation of the computer models, from entirely independent evidence.

The world's governments had created a panel to give them the most reliable possible advice, as negotiated among thousands of climate experts and officials. By 2001 this Intergovernmental Panel on Climate Change (IPCC) managed to establish a consensus, phrased so cautiously that scarcely any expert or government representative dissented. They announced that although the climate system was so complex that scientists would never reach complete certainty, it was much more likely than not that our civilization faced severe global warming. At that point the discovery of global warming was essentially completed. Scientists knew the most important things about how the climate could change during the 21st century. How the climate would actually change now depended chiefly on what policies humanity would choose for its greenhouse gas emissions.

Since 2001, greatly improved computer models and an abundance of data of many kinds strengthened the conclusion that human emissions are very likely to cause serious climate change. The IPCC's conclusions were reviewed and endorsed by the national science academies of every major nation from the United States to China, along with leading scientific societies and indeed virtually every organization that could speak for a scientific consensus. Specialists meanwhile improved their understanding of some less probable but more severe possibilities. On the one hand, a dangerous change in ocean circulation seemed unlikely in the next century or two. On the other hand, there were signs that disintegrating ice sheets could raise sea levels faster than most scientists had expected. Worse, new evidence suggested that the warming was itself starting to cause changes that would generate still more warming.

In 2007 the IPCC reported that scientists were more confident than ever that humans were changing the climate. Although only a small fraction of the predicted warming had happened so far, effects were already becoming visible in some regions — more deadly heat waves, stronger floods and droughts, heat-related changes in the ranges and behavior of sensitive species. (See the summary of expected impacts.) But the scientists had not been able to narrow the range of possibilities. Depending on what steps people took to restrict emissions, by the end of the century we could expect the planet’s average temperature to rise anywhere between about 1.4 and 6°C (2.5 - 11°F).

Some people feared that the IPCC was too conservative; they insisted on emergency measures to avoid the risk of catastrophe if temperatures rose to the upper end of the projected range or even beyond. Others insisted that the IPCC was wholly mistaken; there was no need to worry. They pointed to a minority of scientists (scarcely any of them known for contributions to climate science) who held to the old conviction that human activity was too feeble to sway natural systems. Distrust of the climate experts was encouraged by corporations and political interests that opposed any government interference in the economy. However, the scientists who had been predicting for decades that by 2000 the world would be significantly warmer were now obviously correct. Science reporters, business leaders, government advisers and others increasingly believed them. An ever larger number of individuals, corporate entities, and government agencies at every level decided that something had to be done. They found that effective steps could be taken at surprisingly little cost, and many began to take them.

What do we know today about how global temperature changes?

The temperature of the air near the surface has been measured by land, sea and satellite instruments, very accurately since the 1970s and fairly accurately since the late 19th century (black curve in GRAPH A, below). Four main influences are known, and combining these gives quite a good match to the observations (orange curve in A). The known influences are: irregular “El Niño” fluctuations in the upwelling of deep cold waters in the tropical Pacific Ocean, which cool or warm the air for a few years (purple curve in B); sulfate smog particles emitted in volcanic eruptions, such as El Chichón in 1982 and Pinatubo in 1991, which bring temporary cooling (blue curve); a quasi-regular cycle in the Sun’s activity that changes the radiation received at Earth (green curve); and human ("anthropogenic") changes — primarily emission of carbon dioxide from fossil fuels, but also other greenhouse gases and pollution such as smoke, and land-use changes such as deforestation (red curve). Theorists can calculate the actual influence of each factor, but only approximately. The authors of the model shown in the graph adjusted the weights to give the best fit to the observations. In particular, the global heating since the 1970s can be explained only by humanity’s greenhouse gas emissions. Note, for example, how the temperature trend in the first decade of the 21st century was generally flat because an upward push by anthropogenic forces was temporarily offset by a downward pull as solar activity decreased and the oceans absorbed more heat than usual from the atmosphere (sea water temperatures in fact continued to rise).

 

[Grat3fulh3ad]

Some people appear to imply that by using the word "science" they can influence more people who are not smart enough to know better.

Luckily, I am not merely using the word 'science', but am posting up the actual relevant science which you cannot refute in any meaningful way...

and some people think that ignoring the science, makes it invalid... lol



97% of the people who are smart enough to grasp the science believe in AGW... 'nuff said

 

[SpasticGramps]

I am profoundly disappoint in you man.

I'm sorry I've failed you lol. We disagree on a lot more than this.

We agree that it's a scientific debate. The paradigm rift is some see it as political science other's as physical science.