Is Anthropogenic Global Warming (AGW) a reality?
Or, to put it more simply, are humans responsible for global warming? This is a difficult question to answer, and, right off the bat, we should say that you're not going to get the answer from this article. But, to be fair to us, you're not going to get the answer from any article. The scientific community is more divided than ever on whether AGW is a reality.
There are literally thousands of Phd-level environmental specialists who believe humans are contributing to global warming, but, unfortunately, there are thousands of equally qualified sceptics. Where does this leave the layman? More importantly, where does it leave those required to formulate policy and laws based on the answer? The answer to both questions is floundering.
In this article, we'll present commonly cited facts for AGW and against AGW. It is interesting to note how many of these "facts" are presented like they're unquestionable or how many make an appeal to an unnamed authority (e.g. "It is well documented that...", "It has been proven that...") This is how authority fallacies often start.
After we've presented the "facts", we'll offer the best science-based arguments for and against AGW. If you're anything like us, you'll believe the last one you read. For this reason, we have deliberately not presented the facts side by side, because we want you to adopt a position on AGW in order to test whether you maintain it after reading the opposing argument.
Commonly cited facts against AGW
- On average, the United Kingdom is 1 degree cooler now than it was when the Doomsday Book was written (AD 1086).
- Greenland's name derives from its green pastures that attracted the Norse settlers around one thousand years ago. However, they were forced to leave by the encroaching ice, which is still there.
- Temperature measurements by satellite, radiosonde balloons and well-maintained rural surface stations show no signs of warming. It has been proven that evidence of "significant warming" comes from surface stations affected by a variety of factors that contaminate their data.
- It is well documented that computer models are meaningless, because they offer a broad spectrum of answers which are wholly dependent on input assumptions.
- Reports from the UN's Intergovernmental Panel on Climate Change (IPCC) are behind the global-warming scare. However, it has since been discovered that they doctored their reports to meet their political objectives. After being found out, their latest reports are fair less alarmist, and many of the scientists who wrote the original reports have switched camp.
- AGW relates to the amount of carbon dioxide (CO2) in the atmosphere. CO2 is a minor greenhouse gas. Water vapour, which is the dominant greenhouse gas, is over a hundred times more prevalent. Moreover, without the "greenhouse effect", there would be no life on Earth at all.
- Studies that have checked temperature and CO2 levels over the last 545 million years show no correlation between CO2 levels and global temperatures. In fact, there have been ice ages when CO2 has been as much as 10 to 15 times higher than today (e.g. the end-Ordovician Ice Age). There have also been times when temperature was increasing but CO2 was decreasing (during the Silurian and Devonian ages), and times when CO2 was increasing but temperatures decreasing (during the Triassic and Jurassic ages). Conclusion: CO2 levels do not affect global temperature.
- Do not believe everything you read. More than 4,000 scientists, including 72 Nobel Prize winners, have contested the scientific approach that supported AGW. Most scientists do not believe in AGW, which is why the so many have signed:
- The Statement by Atmospheric Scientists on Greenhouse Warming (1992) [more...]
In 1992 in Washington, a body of leading atmospherics scientists stated:
"As independent scientists, researching atmospheric and climate problems, we are concerned by the agenda for the United Nations Conference on Environment and Development (UNCED) being developed by environmental activist groups and certain political leaders. This so-called Earth Summit is scheduled to convene in Brazil in June 1992 and aims to impose a system of global environmental regulations, including onerous taxes on energy fuels, on the population of the United States and other industrialized nations.
Such policy initiatives derive from highly uncertain scientific theories. They are based on the unsupported assumption that catastrophic global warming follows from the burning of fossil fuels and requires immediate action. We do not agree.
A survey of U.S. atmospheric scientists, conducted in the summer of 1991, confirms that there is no consensus about the cause of the slight warming observed during the past century. A recently published research paper even suggests that sunspot variability, rather than a rise in greenhouse gases, is responsible for the global temperature increases and decreases recorded since about 1880.
Furthermore, the majority of scientific participants in the survey agreed that the theoretical climate models used to predict a future warming cannot be relied upon and are not validated by the existing climate record. Yet all predictions are based on such theoretical models.
Finally, agriculturalists generally agree that any increase in carbon dioxide levels from fossil fuel burning has beneficial effects on most crops and on world food supply.
We are disturbed that activists, anxious to stop energy and economic growth, are pushing ahead with drastic policies without taking notice of recent changes in the underlying science. We fear that the rush to impose global regulations will have catastrophic impacts on the world economy, on jobs, standards of living, and health care, with the most severe consequences falling upon developing countries and the poor." [less...]
- The Leipzig Declaration (1997) [more...]
The 1995 declaration asserts:
"There does not exist today a general scientific consensus about the importance of greenhouse warming from rising levels of carbon dioxide. On the contrary, most scientists now accept the fact that actual observations from earth satellites show no climate warming whatsoever." [less...]
- Oregon Petition (1998) [more...]
The Orgegon Petition, which received the signatures of over 19,000 scientists including some very eminent names, states:
"We urge the United States government to reject the global warming agreement that was written in Kyoto, Japan in December, 1997, and any other similar proposals. The proposed limits on greenhouse gases would harm the environment, hinder the advance of science and technology, and damage the health and welfare of mankind. There is no convincing scientific evidence that human release of carbon dioxide, methane, or other greenhouse gasses is causing or will, in the foreseeable future, cause catastrophic heating of the Earth's atmosphere and disruption of the Earth's climate. Moreover, there is substantial scientific evidence that increases in atmospheric carbon dioxide produce many beneficial effects upon the natural plant and animal environments of the Earth." Do not get the impression we are filling the air with CO2. CO2 is a trace gas in the atmosphere (composing only an infinitesimal .04%). It is essential to photosynthesis and therefore life on the planet. If CO2 levels were cut in half to 200 parts per million, all plant growth would stop. It's no coincidence that commercial green house owners use CO2 generators to increase crop production. [less...]
Some commonly cited facts for AGW
- Humans are pumping huge amounts of carbon dioxide, methane and other greenhouse gases into the atmosphere. The increased concentration of greenhouse gases is raising the temperature of our atmosphere and the Earth's surface. The effect of greenhouse gasses has been repeatedly demonstrated in laboratory experiments.
- It is indisputable that the Earth's climate is changing rapidly. Across the world, people are feeling the impacts of rising global temperatures, including shifting patterns of precipitation and rising sea levels.
- Industry, electric power generation, agriculture and transportation are the leading causes of greenhouse gases. The concentration of CO2 in the atmosphere has risen from 290 parts per million (ppm) in 1900 to nearly 400 ppm.
- In Alaska, western Canada, and eastern Russia, average temperatures have risen by 3 degrees Celsius in the past 50 years.
- Every day, 70 million tons of carbon dioxide are released into our world's atmosphere.
- Since records began (1880), 10 of the warmest years on record have been in the past 12 years.
- Ever since satellites began keeping track (1979), the summer of 2007 saw the lowest levels of Arctic sea ice ever recorded at 1.65 million square miles. This was 860 thousand square miles below the average seen from 1979 to 2000. The melting Arctic ice has opened the Northwest Passage above North America for the first time in 100 years.
- 82% of glaciers have disappeared in Glacier National Park, Montana, where there are now only 27 glaciers compared with 150 in 1910.
So, Where does this leave us?
Notwithstanding the last decade (which protagonists on both sides seem to agree has seen temperatures flatten out), it would seem the world has been getting marginally warmer over the last century, but it is also quite apparent the world has been significantly hotter in the past than it is now. So, are we witnessing a natural phenomenon or are we causing it? That part remains unresolved. It is also fairly clear that CO2 levels are increasing. But, what is less clear is whether global warming is due to increased CO2 concentration or whether the increased concentration is the result of global warming. (The oceans, which contain thousands of times more CO2 than the atmosphere, release massive amounts of CO2 when warmed.) From a studying-bias perspective, it is apparent that one half of the community is anchoring strongly to the increased concentration of CO2 in its calculations while the other half is largely treating CO2 as an irrelevance.
That said, here — as promised — are the best two pieces of science-based evidence we could find. One supports AGW. The other refutes AGW. Sorry about that.
A Decrease in Cosmic Rays Causes Warming
Henrik Svensmark and Nigel Marsh, two Danish cosmic-ray specialists, have shown an indirect connection between galactic-cosmic-ray (GCR) intensity and global temperature. Their study is based on how the Sun influences the flow of GCR to Earth. They assert that high periods of sunspot activity affect the Earth's magnetosphere and allow more GCR to strike the Earth. When the Sun is active, the increased GCR causes more ionization in the atmosphere and, possibly, more cloud condensation nuclei (CCN). (Also called "cloud seeds", they are tiny particles around which cloud droplets coalesce; i.e. a starting point for forming clouds.) The increase in CCN appears to create more low-level clouds, and these cool the Earth. Therefore, when the Sun is less active, the GCR intensity is reduced, allowing the Earth to warm. With terms like "possibly" and "[It] appears to create", their assertion seems a little tentative, but what is undeniable is that Svensmark and Marsh have shown a striking statistical correlation between sunspot activity and global cooling and warming over the past 1000 years. In other words, their reasoning might not be accurate, but their root cause looks statistically extremely plausible. If they're right, CO2 increase is not causing global warming. It's an effect of global warming caused by a less active Sun.
Empirical Evidence That CO2 Causes Global Warming
Sunlight passes through our atmosphere and warms the surface. The surface cools by emitting infrared radiation back towards space. As infrared radiation travels through the atmosphere, some is absorbed by greenhouse gases such as water vapour and CO2. This warms the atmosphere which then reradiates the infrared radiation in all directions. Some escapes to space while some radiates downwards and warms the surface again.
Therefore, with more CO2 in the atmosphere, we would expect to see less infrared radiation escaping to space, and this is happening as confirmed by satellites specifically launched to measure this phenomenon. Significantly to prove AGW, these satellites have detected a reduction in outgoing radiation at the wavelengths that CO2 absorbs energy. This presents "direct experimental evidence for a significant increase in the Earth's greenhouse effect".
There's more. Ground measurements also detect an increase of infrared radiation heading back down towards Earth, and this confirms the increased greenhouse effect. By closely analysing the changes at different wavelengths, scientists can calculate how much each greenhouse gas contributes to the warming effect. The results are consistent with both theory and satellite measurements of the enhanced greenhouse effect, leading to the conclusion that "this experimental data should effectively end the argument by sceptics that no experimental evidence exists for the connection between greenhouse gas increases in the atmosphere and global warming."
Establishing the truth on AGW is going to be difficult. On the assumption the Earth is getting warmer, it is presently unknown whether the warming is the result of one cause or a number of causes, and no one knows how much weight to place on each factor, and it is difficult to see how we're ever going to get to the bottom of that conundrum.