How can we know humans cause global warming?

Question

Honestly, I'm still wavering if I believe global warming is caused by humans or not. If major gaps that control the climate like the one in the linked story are still being discovered, how can we have a definitive, scientific answer?

http://news.yahoo.com/s/nm/20070815/sc_nm/australia_ocean_dc

Answer 1

Global warming is one-half of the climatic cycle of warming and cooling.
The earth's mean temperature cycles around the freezing point of water.
This is a completely natural phenomenon which has been going on since there has been water on this planet. It is driven by the sun.
Our planet is currently emerging from a 'mini ice age', so is becoming warmer and may return to the point at which Greenland is again usable as farmland (as it has been in recorded history).
As the polar ice caps decrease, the amount of fresh water mixing with oceanic water will slow and perhaps stop the thermohaline cycle (the oceanic heat 'conveyor' which, among other things, keeps the U.S. east coast warm).
When this cycle slows/stops, the planet will cool again and begin to enter another ice age.
It's been happening for millions of years.
Humans did not cause it.
Humans cannot stop it.

Answer 2

there is too much we still don't understand for there to be anything you would call a definitive answer. you are asking for proof that there is no way it could be anything else. we can't do that any more than we can prove, beyond a doubt, that aliens didn't build the pyramids.
what we can do, is say all we know points towards human causes - read answer above for some basics. and with serious, irreversible damage predicted in the next 50 years, do we really have the time to wait for undeniable proof? or should we be looking for energy sources that don't rely on carbon, good fertile ground to reforest, and millions of other small ways to slow this down?
nobody can give you proof positive that this isn't somehow caused by a natural phenomenon we are unaware of. what we can say is that we are able to trace temperature change back through the centuries, and if this is a natural cycle, it's one that has never happened before.

Answer 3

We know how greenhouse gases work - they have a simple physical property that prevents heat escaping from the atmosphere. The insulate the planet and if there were no greenhouse gases Earth would be so cold that life would never have evolved.

Manmade and natural greenhouse gases are identical (apart from the small volume of purely synthetic ones). Any increase in atmospheric concentrations of this gases inevitably leads to higher temps. Quite simply, it's a physical impossibility for that not to happen.

Another thing we can do is to look back over millions of years of climate history and see how things have been in the past and compare that to what's happening now. When we do that we see that there has been historical warming and cooling, often on a much larger scale than we're seeing now but never at even close to the speed at which things are currently changing.

To put it into persepective, the end of the last ice age came about because of an incredibly rapid natural rise in temperatures - some 7°C in 7,500 years. When we look at how fast temps are rising now we see that it's 19 times as fast. This is no surprise or mystery, it's been understood for a long time and predicted for even longer.

Answer 4

honestly... theres no way of actually determining if global warming exists and if humans are directly related to causing it.

it could just be the earth is heading towards another ice age ( as previous records have shown the earth heats up before an ice age) or it could be that the carbon pumped by humans is causing the earth to warm up

Answer 5

I agree with orange jello up there - we don't.. but it is like they say - it's better safe than sorry. What harm does going green do? Is it really a bad thing to enforce an effort that even if it doesn't turn out to stop global warming, helps to put less of an ecological foot print, cleans our air, cleans our planet, and leaves our planet in a better place for our children then it was left to us?

Answer 6

When I was in the army I saw this alot. When something goes wrong, people are more worried about placing the blame rather than finding a solution. Does it really matter wether we caused it or not? It is happening and we know that our actions do contribute to it.

We know that global warming can have catastraphic affects, so we had all better start doing our part.

Answer 7

How can we know cigarette smoking causes cancer?
We all know it does, but a few decades ago people weren't so sure, and a few decades before that almost everybody in the US smoked. With so many politicians and special interests producing their own "experts", these things take time to become accepted. No amount of scientific certainty is going to convince people who aren't going to listen.

Answer 8

Because the circus ringmasters like Algore, John Edwards and such say so from their gigantic mansions and their private jets. If you cant believe them, who CAN you believe?

Answer 9

it's climate change..people want to rush in to making a judgment about it instead of taking of taking their time and making their decisions based on facts..they didn't keep accurate records hundreds of years ago..they didn't have accurate thermometers a hundred years ago..there are so many unanswered questions about this subject..slow down and take their time to get it right..this is a religion and not a scientific facts that they're pushing on us..I'm not naive so get the facts first

Answer 10

Good question. Quick answer - we don't. If you have to 'believe', then you are involved in religion, not science.

Wait until science and prove what is happening so we can take proper action. View my prior post to see what happens when we take knee jerk, feel good action based on our emotions, and not facts.

In time we will know. Our scientist are lazy and looking for immediate gratification, so they rush their opinions and put them up as facts.