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Global Warming - It's Real, And We're Causing It

Global WarmingI was with a group of people yesterday, and one of them brought up the recent news of the U.S. listing polar bears as a threatened species under the Endangered Species Act, due to their expected decline as global warming melts the arctic sea ice they depend upon for survival. And of course, this got the conversation going on global warming. Out of the six of us, one guy thought that scientists just didn't know what the hell was going on with the climate, that there wasn't any real consensus on global warming at all, and that even if global warming were real, which he doubted, polar bears would find a way to survive, anyway. Another guy seemed more open to the idea that global warming could be happening, and could be human caused, but wasn't entirely convinced. I tried my best to defend the science, while the other three people stayed pretty quiet on the subject (although from a previous conversation, I think that one of them at least accepts that global warming is happening). Later on, when I told another guy about this conversation, he seemed to think that the current global warming might just be a natual cycle, and that it's not human caused. So, out of 7 people, I was the only one to strongly accept that current global warming is human caused.

Now, I'll admit I'm no expert on global climate. Not only am I not involved with the field at all, but I haven't really studied it in depth on a lay level, either, like I have other fields such as evolution. So, I guess I need to ask myself, how can I go on accepting that humans are causing global warming, and that it is a major problem?

First, I'll defer to the experts. I realize this isn't exactly a sound logical approach - after all, evidence is evidence no matter who discovers it. But, in the same way that I'll take my doctor's advice on what effects different medicines and procedures have, I'll put a fair amount of weight on the statements of the people who devote their careers to studying climate.

First, let's take a look at the UN's Intergovernmental Panel on Climate Change (IPCC). Their 2007 report has a Summary for Policy Makers (pdf), detailing their key findings, which contains statements such as these:

Warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice and rising global average sea level.
Global GHG [greenhouse gas] emissions due to human activities have grown since pre-industrial times, with an increase of 70% between 1970 and 2004.
Global atmospheric concentrations of CO2, methane (CH4) and nitrous oxide (N2O) have increased markedly as a result of human activities since 1750 and now far exceed pre-industrial values determined from ice cores spanning many thousands of years.
Most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic GHG concentrations. 7 It is likely that there has been significant anthropogenic warming over the past 50 years averaged over each continent (except Antarctica).

So, here's a group composed of hundreds of scientists from dozens of countries, working on a report that needed to be approved by all of them. Even without having a great understanding of the science, I'd put a fair amount of trust in a report prepared that way. But, say you don't like foreigners, and you want some stuff done here in the good old U.S. of A. How about NASA's Goddard Institute for Space Studies? The day I checked their site, their lead story was Earth Impacts Linked to Climate Change, with the summary:

A new study shows that human-caused climate change has impacted a wide range of natural systems, from Arctic permafrost thawing to African lakes declining in productivity.

They take human-caused climate change as such a given that they're simply moving on to addressing its effects.

How about the Environmental Protection Agency? Well, they have a whole site devoted to Climate Change, but let's take a look at their frequently asked questions, specifically this question, Are human activities responsible for the warming climate?. Here's their response:

Careful measurements have confirmed that greenhouse gas emissions are increasing and that human activities (principally, the burning of fossil fuels and changes in land use) are the primary cause. Human activities have caused the atmospheric concentrations of carbon dioxide and methane to be higher today than at any point during the last 650,000 years. Scientists agree it is very likely that most of the global average warming since the mid-20th century is due to human-induced increases in greenhouse gases, rather than to natural causes.

The National Oceanic and Atmospheric Administration has a section on this, too. Here're some of the things they have to say:

Human activity has been increasing the concentration of greenhouse gases in the atmosphere (mostly carbon dioxide from combustion of coal, oil, and gas; plus a few other trace gases). There is no scientific debate on this point.
Global surface temperatures have increased about 0.74°C (plus or minus 0.18°C) since the late-19th century, and the linear trend for the past 50 years of 0.13°C (plus or minus 0.03°C) per decade is nearly twice that for the past 100 years. The warming has not been globally uniform. Some areas (including parts of the southeastern U.S. and parts of the North Atlantic) have, in fact, cooled slightly over the last century. The recent warmth has been greatest over North America and Eurasia between 40 and 70°N. Lastly, seven of the eight warmest years on record have occurred since 2001 and the 10 warmest years have all occurred since 1995.

There's also a "Joint science academies’ statement: Global response to climate change" which was signed and endorsed by the Academia Brasiliera de Ciências, the Royal Society of Canada, the Chinese Academy of Sciences, the Academié des Sciences of France, the Deutsche Akademie der Naturforscher of Leopoldina, Germany, the Indian National Science Academy, the Accademia dei Lincei of Italy, the Science Council of Japan, the Russian Academy of Sciences, the Royal Society of the United Kingdom, and the National Academy of Sciences of the United States of America. Some of the wording in that statment includes:

There will always be uncertainty in understanding a system as complex as the world’s climate. However there is now strong evidence that significant global warming is occurring1.
The existence of greenhouse gases in the atmosphere is vital to life on Earth – in their absence average temperatures would be about 30 centigrade degrees lower than they are today. But human activities are now causing atmospheric concentrations of greenhouse gases – including carbon dioxide, methane, tropospheric ozone, and nitrous oxide – to rise well above pre-industrial levels. Carbon dioxide levels have increased from 280 ppm in 1750 to over 375 ppm today – higher than any previous levels that can be reliably measured (i.e. in the last 420,000 years). Increasing greenhouse gases are causing temperatures to rise; the Earth’s surface warmed by approximately 0.6 centigrade degrees over the twentieth century.
1 This statement concentrates on climate change associated with global warming. We use the UNFCCC definition of climate change, which is ‘a change of climate which is attributed directly or indirectly to human activity that alters the composition of the global atmosphere and which is in addition to natural climate variability observed over comparable time periods’.

So, if we're to trust the experts, there is an overwhelming consensus that global warming is real, and that us humans are the ones causing it.

But, reality isn't based on a vote, so let's take a look at at least a little of the data to back up these claims. I found a site that puts the data into nice, easy to see graphics, Global Warming Art. Here's a graph of carbon dioxide concentrations over the past several thousand years:

Carbon dioxide concentrations in the atmosphere over both the last 1000 years and the preceding 400,000 years. Over long times, carbon dioxide influences and responds to the ice age cycles.
Image from Global Warming Art.

Here's a graph of reconstructed temperature, which seems to show a pretty good correlation to those carbon dioxide levels (note that it goes back just a little farther into the past than the above graph).

Changes in Antarctic temperature and ice volume during the last four glacial/interglacial cycles
Image from Global Warming Art.

And just to show that the scientists really do have a pretty good understanding of what's going on, here's a graph showing model predictions compared to actual measured global temperature:

Climate Change Attribution
Image from Global Warming Art.

So, as stated above, there seems to be a huge consensus among the people actually studying the issue that global warming is real, and that us humans are the ones causing it. The data available certainly seems consistent with what they're saying. So, I really don't understand how people could doubt global warming, unless they're just not willing to look into it.

For those wanting to research this more (as I certainly plan to), the Global Warming Art page looked pretty good. Also, RealClimate looks to be a pretty good resource, especially their page, Start here. They even have a section of links to sites dealing with correcting misconceptions raised by "contrarian talking points." A couple of the ones I've already looked at are How to talk to Global Warming Skeptic and Anti-global heating claims - a reasonably thorough debunking. And finally, just follow the literature. I read the Nature News site every day during my lunch break. Nature's a very reputable journal (note - the News site isn't publishing peer reviewed research like the journal, itself, but it must still uphold the same reputation), and in the past 5 years or so since I've been following that site, with all the articles on global warming that they've published, I haven't seen a single one that called into question global warming or that we're the cause of it.

All images in this entry came from Global Warming Art.


good post Jeff. I'm finding that same reaction among many people in my sphere. Towards that end, I created a new digital atlas showing the causes, potential effects, and solutions to global warming. Check it out here:

That icecore graph does not have the resolution to show that temperatures causes the C02 release not the other way around. In other words, you can use the C02 gauge to measure temperature but not the other way around.

The fact that we are releasing a byproduct of warming does not suggest that we will experience warming as a result.

And good job noticing the ad hominem fallacy, hopefully you will look even deeper into the logic of all this.

I'm always amazed the things that people don't believe in. I took a speech class about a year ago and arbitrarily chose global warming as my topic. We could choose anything as long as it was something that was debated. I mostly chose it because the wealth of info on it would make finding sources easy.

Out of my class of ~20 college students, I was one of a few that "believed" in global warming. About half didn't believe because the earth was only 6000 years old. Some believed that it was a sign of the apocalypse. In defense (sort of a defense I guess) of some, it wasn't that they didn't believe in it, they just didn't care and never even thought about it.

After my disbelief wore off, I inquired how many believed in evolution. Being that my college was at a community college in the bible belt, and their previous track record, I doubt I have to say how many people believed it. My next speech was on the scientific process, and the following one after that was on the age of the earth.

I think I wasted my time (except for the good grade of course) on all of them. I don't think many of them even considered what I talked about, and I doubt any of them changed their mind. They all thought I was a super genius, even though I didn't mention anything you couldn't learn from a 5th grade education or a few hours googling. It was rather disheartening, especially when you consider that it's the norm.

Oh, another thing, Global warming art was the website I got all my graphs from for my speech. Great website. I love the glaciers then and now shots.


The greenhouse effect is not in dispute at all. This effect was discovered way back in the 1800s, and has only become better understood since then. And it's not just a phenomenon on Earth - it's also known to be the mechanism responsible for Venus being as hot as it is.

Carbon dioxide is a greenhouse gas, period. There's no point in arguing that. There may indeed be feedback mechanisms involved, but if increased temperatures caused more CO2 to be present in the atmosphere, that would only increase the greenhouse effect, and cause even higher temperatures. (To be honest, if I were going to attack those two graphs, it wouldn't be the correlation vs. causation - I would go right to the source and ask how we can know temperatures from the past. CO2 concentrations seem pretty straight forward, but temperature? That's something I plan to research more in the future.) However, the fact of the matter is that greenhouse gas concentrations, particularly those of CO2, are increasing, and effects of global warming have already been observed.

Finally, I'd like to address the ad hominem fallacy a bit, since it's become a bit of a pet peeve of mine now that I've seen the term tossed around so much in Internet debates. Ad hominem arguments, and the related Appeal to Authority arguments, or argumentum ad verecundiam are logical fallacies. You can't say that a particular claim is true or false just based on the person making it. In particular, in the midst of a debate, you should address your opponents arguments, and not resort to name calling or questioning their integrity, or to touting your own credentials.

However, in the larger view in the real world, people do have reputations and expertise. For example, if you get sick, you could go to a snake oil salesman or a doctor. Most people would choose the doctor because of their expertise. Of course it's an appeal to authority to accept the doctor's diagnosis. Just because the doctor tells you something doesn't mean it's necessarily true, yet most people trust their doctors because of the years of training they've received, and the years of experience they have practicing. It may not be "logical" to accept the doctor's diagnosis, but it still makes sense to do so. Carrying on the doctor analogy, doctors can and do make mistakes, so people will often times seek a second opinion. Even with the expertise and reputation individual doctors have, patients will seek a consensus. Once a few doctors have looked at a patient and made their diagnoses, 99 times out of a hundred they'll be right.

I get this problem a bit in my field, as well. I'm an aerospace engineer, working on a project to make a high speed VTOL vehicle, using a rotor for takeoffs and landings, and slowing the rotor in flight to reduce drag. Almost invariably, when I first tell people of our concept, they ask why we don't just stop the rotor. There are, in fact, very good reasons to keep the rotor spinning, but it requires a little more detailed knowledge of aerodynamics and structures than most lay people possess, no matter how intelligent they are. Usually, a quick explanation is enough to explain it qualitatively, but it definitely shows the value in having expertise in a field. (I could also add, that I got so tired of seeing the oft repeated claim of how wings create lift, that it prompted me to create an Aviation Theory section on my website.)

Even though expertise and reputation are useless for logical arguments, in a world of finite resources, with a limited ability to perform experiments and gather data on our own, they're still very useful tools for sifting through the mountains of information we encounter. So, even though an overwhelming consensus among those studying global climate is not proof that anthropogenic global warming is real, it certainly makes for a very strong case. Add to that the fact that what research I have done into the issue seems to back up what the scientists are saying, and it's going to take some very strong evidence to convince me that anthropogenic climate change isn't occuring.

PB - any blog that has good science AND a picture of Shiner is okay in my book.

Eric - you never know. For the people who'd never given much thought to the science behind those issues before, you may have at least gotten them thinking.

Yeah, hopefully one of them thought about it, or at least decided to look at the world a little closer. The evolution speech was a little fun anyways. We had to have a visual aid, and I couldn't think of a really good one besides just pictures or graphs. Nothing that would really grab their attention. Then it hit me, I could very easily explain the process of natural selection. I took a big bowl and filled it with candy. I put two types of candy, M&Ms and some funky looking wierd black licorice candy I got at the dollar store, in the bowl together. As I was setting up to speak I gave the bowl to the class, and asked them to pass it around and to help themselves to the candy. Towards the end of the speech, I collected the bowl, which now had significantly less M&Ms, and probably the same amount of licorice. It was a great example, especially when explained that the candy didn't "choose" to be the flavor it was, but by "chance" happened to be that way.

I think it would be really fun to be a science teacher. It's a shame that you make so little doing it. I wonder how much better our schools (and society) would be if we took just one months worth of the military's budget and put it towards teachers salaries or retirement, or something of the likes.

I do have one caveat for the seventh guy (myself). He believes that human's are partial or even possibly predominate blame for global warming, but not the entire cause.
Good write up Jeff

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