Global Warming: What Is The Evidence?

What is the actual evidence that a) Global Warming is real, b) it is being exacerbated by human activity, and c) it is not simply a normal weather cycle for the planet that will work itself out? Is the general scientific consensus that Global Warming is real and is being caused by humans?

I ask because while I think global warming is real and is caused by humans, I have not followed the issue closely, and when talking with skeptics about global warming and too much CO2 they will say things such as:

“CO2 only makes up less than one-half of one-tenth of one percent of the atmosphere. In 1950, for every 1 million parts atmospheric parts, 300 were CO2. Aka for every 10,000 parts atmosphere 3 parts were CO2. Today, 70 years later is 4 CO2 per 10,000 parts atmosphere.”

If anyone knows some good literature I can read on the subject - especially if it responds to popular or trenchant objections, please let me know.


Temperature readings conducted over decades and spanning the globe show so.


See below:

As long as we keep emitting more CO2 (and other greenhouse gases) into the atmosphere our planet will keep getting warmer on average.

Tell your skeptic friends that CO2 is a greenhouse gas which is its most relevant feature in the context of climate change. It can absorb and re-emit infrared radiation back to the earth, an ability not possessed by nitrogen and oxygen (both of which make up ~99% of our atmosphere). There is a base warming rate due to the presence of a certain concentration of CO2 and other greenhouse gases like water vapor, however, human activities have increased the concentration of CO2 and that has consequently increased the rate of warming.

There are many good resources on climate change. NASA, NOAA etcetera all have excellent materials on climate change related topics. Don’t forget the IPCC reports like the one below:


Hi @LyghtWayve -

That’s a very good question. It turns out that global temperature is very sensitive to CO2 concentration. Here is a visualization of historical data gathered by geophysicists:

Source: Temperature Change and Carbon Dioxide Change | National Centers for Environmental Information (NCEI) formerly known as National Climatic Data Center (NCDC)

Note that a change from 3 parts in 10,000 to 4 parts in 10,000 is also a 33% increase in concentration. The absolute values are irrelevant; the change in concentration is what strengthens the greenhouse effect.

Here’s a useful analogy: It would only take a drop of snake venom in my 6 liters of blood to kill me. Compared to atmospheric CO2, a drop of snake venom would be a far lower concentration.

Note that a concentration of just 280 ppm CO2, when it was sustained for millenia, resulted in temperatures 6o C. warmer than today. That’s 11o F.! And today’s atmospheric CO2 concentration is about 420 ppm! Fortunately, it would take millenia for that extraordinarily high equilibrium to be reached, so we have time to avert the very worst climate consequences of global warming if we act corporately, quickly, and intelligently.

Chris Falter


The global warming discussion comes down to a series of questions, some independent of one another:

  1. Is the earth warming?
  2. Is human activity contributing?
  3. Is warming bad?
  4. Can we do anything?
  5. Should we do anything?

  1. Humans have increased atmospheric CO2.
  2. CO2 is a greenhouse gas.

That’s it, that’s all you need. That tells you the answer to questions 1 & 2 is a resounding YES!

It does not provide an answer to the remaining questions.

This would require that one of the two things above be false, and neither is false.

It is absolutely the consensus of scientists in relevant fields that it is real and that humans are contributing.

Start at the beginning:


Others are far more knowledgeable about this than I am so I’ll be brief: isn’t that statement actually a very strong argument FOR anthropogenic global warming? A 1/3 increase in CO2? That sounds immense. I would think that’s precisely the sort of thing I would NOT say if I were trying to pooh-pooh it.

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That’s a 33% increase in CO2, and due to human activity. That’s huge and should already be a cause for serious concern.


Thanks for these resources.


Thanks for your replies everyone. This is really helpful.

I am just amazed at how today people will listen to any critic of scientific consensus, and then swear they have facts and knowledge and now know more than practicing experts. It’s amazing to me.

For example, one person I know is staunchly anti-vaccine. I always ask him, what do you know that practicing virologist, immunologist and epidemiologist don’t know. The answer is always incoherent or he will send something that is debunked by scientists.

To be honest, I don’t know how we got to this point as a society. How did we get to the point that so many people think their untrained opinions and/or folks on social media with no training or grasp of the relevant sciences know vastly more than trained practicing scientists, health officials and entire professions. Perhaps the most shocking example is when someone in Texas thought the snow storm earlier this year was fake ice because it did not melt. In. America.

Yet, what I also find fascinating is when these same individuals need help, the first place they run to is the hospital to be treated by the very scientists who they claimed were wrong.

I have learned over the past year that you can convince humans of anything. You can even convince humans to not see what is directly in front of them, or to see something that is not there. You can convince humans to bring about their own demise, and you can convince humans to delude themselves or believe any lie.

The science and observations that debunk these conspiracy and anti-science views are widely available yet folks lie and say there is no science to support the consensus position. For example despite volumes of studies showing mask and vaccine efficacy, people will go on social media and get tens of thousands of likes for saying there is no science to support mask wearing or vaccine efficacy.

What I have started to do in my discussions with folks is just ask them for the science behind their position and I will accept nothing less. Don’t get me wrong, I am not into scientism - the belief that science is the only valid way or the most effective way to know reliable truths about reality. However, what I find is that the position of science-deniers and anti vaccine folks is so abundantly and easily contradicted by the science that their positions are easy to refute.

At any rate, I digress. Returning to climate science, I will be diving into the information shared on this thread.


Just one thing I’d like to add to the many good posts already is that methane (CH4) is also a potent greenhouse gas also produced by human activity, mostly by all the livestock we use for food, and also significantly contributes to global warming.

The one good thing about methane compared to CO2 is it degrades much more quickly, so once it’s source is removed it should disappear in a matter of decades. So if we can significantly reduce methane production it should relatively quickly have an effect, whereas CO2 is known to persist in the atmosphere for centuries.

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I helped in making this video:


Thanks very well done!

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