Climate Change - How do we know humans cause it?

How is the causation of climate change demonstrated to be caused by humans? How do we know that the climate change isn’t just a natural change in the enivorment?

In terms of proof, like in a court of law, we can’t know, because we simply don’t understand enough about the Earth and its climate.

In terms of collecting evidence in favor of an anthropogenic cause for climate change vs. a natural cause, we know that humans produce x billion tons of greenhouse gases and release them into the atmosphere. We also know that these gases cause the Earth’s system to retain heat and the Earth’s climate to become warmer on average. The evidence is circumstantial.

We know that humans are pooring vast amounts of gasses such as CO2 into the atmosphere. We know that such gasses can affect climate. We do not know what kinds of changes will eventually arise or the severity of those changes.

By merely existing, we affect the environment and thus the climate, as does every other living thing. The real question is do we significantly affect it? The simple answer is that we don’t know. Read Bjorn Lomborg’s The Skeptical Environmentalist for a comprehensive debunking of many - but not all - the scare stories. There are clear cases where we have totally fucked things up - the Aral Sea is an obvious case, as is over-fishing, but one good volcanic eruption throws an awful lot of polution into the upper atmosphere. Krakatoa affected the global climate for years. The northern Atlantic area is not as warm as it was 1000 years ago when Greenland was settled and southern England was a major wine-producing area.

Ask, read, and form your own opinion.

Global warming (as caused by humans, and maybe even in general) is vastly overrated and hyperbolic.

Let me explain.

Firstly, the doomsayers who are at least keeping themselves moderately realistic report a net increase of .45 C over the 20th century. In terms of global climate change, that is a pretty decent increase.

However, the reporting method most commonly used is hopelessly flawed.

The methods researchers have used to record this .45 C increase are based on land-based monitoring stations. And unfortunately a disproportionate number of these stations are in urban areas.

IN these urban areas, there is an exaggerated increase in temperature because of the urban heat trap. Basically, the horizontal planes of concrete (roads) combined with the verticle planes of concrete (skyscrapers, tall buildings) trap heat in urban areas and show a temperature that is higher than it normally would be in that area sans the human development.

Satellite temperature monitoring systems have shown a far different picture than land based monitoring systems. A picture that is often hidden from you, they show a picture of very small to moderate (.15 C) global warming over the 20th century, and a period of global COOLING in the mid 20th century.

It is a well known fact that greenhouse gasses in increased numbers contribute to heat retention globally.

Do you guys know where greenhouse gasses come from in nature? They are a byporduct of photosynthesis. Every plant on the globe is producing greenhouse gases.

And guess what, plants account for 98% of all greenhouse gas emissions. The other 2% is attributable to us.

So even if global warming was as dire as some doomsayers are claiming (.45 C over 100 years) we can’t even attribute much of that to humans, and even if we stopped ALL of our greenhouse gas emissions that would only eliminate 2% of the problem.

So, while heat retention seems to be caused by plants, there has to be more than just “man” that is causing global warming. Because the planet has gone through drastic global temperature changes many many times in its history.

And it is arrogance on our part to think our measly 2% really affects the enormity that is mother nature.

One theory I have heard is that global warming is mostly affected by the sun.

This makes sense to me. If the sun is putting out more heat, there is more heat to be retained due to greenhouse gasses.

Here’s an article explaining the urban heating aspect, which flaws ground based temperature stations:


Here’s a NASA report that vigorously defends the accuracy of the satellite numbers:


However the global warming lobby has been fairly illogical in all of this.

Awhile back they declared BOTH the gound and satellite based measurements to be accurate. But did nothing to account for the disparity. Obviously both cannot be correct.

And the preponderance of evidence shows that there is a much greater chance of flawed monitoring with land based measurements.

I should say, however, that just because it is unlikely our pollution hasn’t caused global warming, that doesn’t mean it isn’t harmful.

Air borne pollutants and reckless industrial waste DO hurt the environment, probably not on the level or in the way that global warming advocates report, but it can seriously impact our society and it should be dealt with.

How do you arrive at your assessment of who is being ‘realistic’? The figure you provide seems to be about the smallest end of most estimates.

I presume that this picture is being so well hidden from us that you can’t provide a cite?

One does not necessarily follow from the other.

OK, so you beat me with the cites…

However, I don’t understand how the satellite readings can give a century-long measurement

I know who is being realistic because based on many of my readings, including the cites I listed prior to your posting, that satellite based recordings are much more accurate and cannot fall victim to the urban heat traps.

The .45 C increase is in the middle of the spectrum, global warming advocates estimate .30 to .60 C increase, the most commonly reported in serious scientific publications is .45 C.

I’ve seen .15 and low reported by satellite imagery. And I’ve seen credible, very credible evidence that the sun is having a huge impact on global warming.

Anyways, I’ve provided enough cites to show my ideas have scientific acceptance, I won’t research the matter for you. Google is a valuable tool, do searches on “urban heat traps and global warming”, “sun and global warming”, and “satellite temperature and global warming.” And you can read and assess the information and come to your own conclusions.

IIRC (it’s been awhile since I’ve been in a global warming debate so I don’t remember everything with 100% accuracy) satellite data goes back to the 70s.

We can compare the satellite recordings for say, the year 2000 with the temperature recordings from the year 1900 and see how much the temperature has increased.

Unfortunately of course, the year 1900 wasn’t a time in which temperature recordings were all that great. Land based recordings are flawed NOW, back then they were compiled via amateur enthusiasts recording temperatures with common thermometers and sending the data in. In some cases the temperature figures are just a composite from many major newspapers around the world.

Unfortunately this really gives us no clear idea as to what the world’s temperature was back then. But from the info we DO have it shows a very small increase since that time, according to satellite figures, anyways.


How does the accuracy compare with dendroclimatology?

GorillaMan: Search for urban heat island

Martin Hyde: Are you sure that plants emit 98% of greenhouse gasses? Is that CO2?

The basic concept is simple. We are putting things into the atmosphere that absorb more of the sun’s energy. The Law of Conservation of Energy tells us that the earth will either get warmer or start spinning faster.

Core samples from glaciers show that humans have had a positive net effect on the level of CO2 in the atmosphere since the invention of fire.

There is a strong correlation between average global temperature increase and the atmospheric CO2 level. The current causes of additional CO2 are dominated by those due to human activity.

The next level is a little more complex. It is a natural human reaction to say, “What’s a few degrees of temperature difference. So it’ll be 85 degrees instead of 80. That’s a pain in the neck, but not the end of the world.”

To a first order approximation, temperature is a measure of weather volatility. The earth will not heat up uniformly, due to the differences between land and ocean and the differences between latitudes. This means larger temperature differentials, which is what causes dramatic weather events like hurricanes, tornadoes, droughts and even blizzards.

The confusing part the average person is that an average global temperature increase can result in localized temperature decreases.

A few degrees Celsius temperature increase is bad. More than that could be catastrophic.

There are some details of the climate which we are unsure of.

Example: Average temperature increases will cause additional cloud formations. Will this mitigate further temperature increases by reflecting more sunlight or will this exacerbate it by insulating the earth’s heat?

Example: The deep ocean currents remove large amounts of CO2 from the air and store them deep under the ocean. Will this process be increased or decreased by a temperature increase?

Example: Is the temperature increase caused by human activity being aggravated or diminished by the natural geological temperature fluctuations of the earth?

I am a scientist but not a climatologist. My reading of independent scientific studies indicates that over the next century, the temperature increase has a 25% chance of being awful, a 50% chance of being devastating and about a 25% chance of being “Game Over”.

Howsabout a cite for that? Plants absorb CO[sub]2[/sub] and emit water vapor. Water vapor is a greenhouse gas, but it is virtually impossible to separate out the contirbution to overall atmospheric water vapor levels from plants from the contribution from plain old evaporation. Other greenhouse gases included methane (which plants don’t emit), ozone (which plants don’t emit), nitrous oxide (which plants don’t emit), hydrofluorocarbons (which plants don’t emit), perfluorocarbons (which plants don’t emit) and sulfur hexafluoride (which plants don’t emit). And those last three - which are entirely man-made - are far more heat absorbent than CO[sub]2[/sub].

According to your second cite, satellites measure temperatures higher up in the atmosphere, so they don’t necessarily need to agree with ground measurements. Current models do predict that they have similar trends, but your cite points out specific shortcomings of the standard model that can account for the difference. Nowhere does it say ground measurements are less accurate than satellite data.

I admit I don’t know much about the heat island effect, but if it’s one of the accepted theories, it’s strange that your second cite does not mention it as a possible explanation. Can you point us towards a peer-reviewed article that says heat island effect can explain the observed temperature increases?

You mean plants absorb greenhouse gases, don’t you?

Photosynthesis simplistically works like this:

6CO[sub]2[/sub] + 6H[sub]2[/sub]O —(sunlight)—> C[sub]6[/sub]H[sub]12[/sub]O[sub]6[/sub] + 6H[sub]2[/sub]O + 6O[sub]2[/sub]

Much of the carbon in a primary producer’s body comes from the atmosphere or ocean, not the other way around.

Producers do also respire (essentially the opposite of photosynthesis), but they cannot respire more than they photosynthesize because then the tree in your back yard would grow smaller and smaller each year until it vanished, rather than growing.

After producers die, then greenhouse gases like CO[sub]2[/sub] can be released, for example if humans were to burn coal, oil, or wood - the geological product of ancient (in the case of wood, less than ancient) producers. Even in that way, plants do not produce 100% of greenhouse gases because many anthropogenic greenhouse gases do not occur in nature (sulfur hexaflouride - HF[sub]6[/sub], for example).


Meant to show:

6CO[sub]2[/sub] + 12H[sub]2[/sub]O —(sunlight)—> C[sub]6[/sub]H[sub]12[/sub]O[sub]6[/sub] + 6H[sub]2[/sub]O + 6O[sub]2[/sub]
Murphy’s law dictates there must be at least one error in my correction, so heer gseo. :smiley:

I was correctly corrected, no, plants do not account for 98% of greenhouse gas emissions. It is more correctly phrased that 98% of all greenhouse gas emissions are attributable to natural causes.

This includes things like volcanic eruptions and other such things which produce quite a lot of greenhouse gases.

If you isolate individual greenhouse gases you may find that humans are responsible for a large percentage of the emissions of that particular gas. But greenhouse gas emissions in their totality are 98% the fault of humans.

Furthermore I should remind everyone that the greenhouse effect is vital to life on this planet, and without it, everyone and everything on this planet would be dead in short order.

  1. The urban heat trap isn’t theory, it is scientific fact. It is easily proven and I’ve provided all the cites I’m going to on this. The idea of urban heat traps is so common and universally accepted I won’t defend it with more cites, there is a point in a discussion where continually asking for cites on issues that are commonly accepted as fact becomes meaningless.

It’s like asking for a cite when someone mentions the theory of relativity in a discussion about physics.

  1. An interesting sidenote, most of the temperature increase of the 20th century occurred prior to 1940. However, most of the increase in greenhouse gas emissions in the 20th century (80%) occurred after 1940. The preponderance of the increase occurred between 1940 and 1970 (which correlates to a period of rapid industrialization with much lighter regulations than today) however from the period 1940 to 1970 global temperature actually had a slight decrease.


Interesting thing to ponder, there. If there is a direct correlation between temperature and increased gas emissions, then it obviously isn’t the strongest of the factors that attribute to global warming.

As for the viability of ground based measurement techniques versus satellite measurement techniques. Except for people who are very strictly attempting to push an agenda, the satellite techniques are considered the standard and are more commonly accepted than anything else.

Most official sources will use satellite figures, and have since 1970. Honestly about the only time you exclusively hear reports from ground based stations is when people need to push the global warming agenda.

Unfortunately in the scientific community there has long been a bit of a chicken little effect in regards to climate change.

During the cooling period seen mid century, some of you may remember scientific worries that we were entering a “new ice age” (this was also blamed on mankind.) Obviously we weren’t, and the cooling during the mid-century was a global cooling period that science could not explain and still cannot explain.

If you notice during 1998 when there was drastic El Nino variations the news about global warming reached its climax in recent memory. If not for the Kyoto Treaty (amazingly coming around the same time as the El Nino mass hysteria, strange coincidence) the issue of global climate change would yet again be far on the back burner and peripheral of public interest.

Unfortunately there are many people who profit from lying about global warming.

Scientists profit by misrepresenting facts because they get to continue researching with big grants given out by hysteria-filled governments worried by ominous climatologist’s reports.

Many environmentalist organizations are simply anti-industrialist without rhyme or reason and will say and do anything to hurt industrialists because they associate them with a form of evil.

From the BBC’s website


Unfortunately climate change has become a political issue. There is a degree ( :slight_smile: )of difference between the views of different scientists on the extent to which it is occurring, illustrated by the variations in the predictions cited above. It is without doubt possible to find scientific cites which support your particular view point. After all, it was not so long ago that cigarette companies were funding scientists to support the morality of their industry. That was a scientific debate with a more clear cut answer. Nonetheless it is the *majority * view point in the scientific community that human behaviour in the form of gas emissions and deforestation is causing climate change. There is not complete agreement, however, so I imagine that we are more likely to arrive at a Great Debate here than a Factual Answer.