If humans are responsible for global warming, what caused previous temperature increases?

Answer 1

Natural cycles - more precisely, orbital (Milankovitch) cycles.

According to these cycles, we should be in the middle of a cooling period right now.

"An often-cited 1980 study by Imbrie and Imbrie determined that 'Ignoring anthropogenic and other possible sources of variation acting at frequencies higher than one cycle per 19,000 years, this model predicts that the long-term cooling trend which began some 6,000 years ago will continue for the next 23,000 years.'"

Answer 2

Well I have been this very subject lately and it is an ongoing debate. Many different sources say different thing, mainly that this is a natural occurance and over time global warming will decrease, but some people are saying that the occurance of this is natural, but we have rose above and decreased in temperature more then any other time period within 600 000 years which is the reason for concern with global warming. There are many reasons people believe that the temperature is increasing, the main reason thought is radiation from the sun causing havock with the earths atmosphere.

Answer 3

There are a variety of natural causes. Variations in solar output has been a cause at times. volcanic activity also--although it tends to lower tempratures short-term. Long term climate pattern shifts can reach a "tipping point" and shift the ovrall trend of warming or cooling.

However--all of these are (by human standards) very slow processes--they take thousands of years. Scientists have examined all these factors (and others I didn't mention) as possible causes--and found that they don't account for our current global warming.

The big difference--other than the fact that the global warming we are now facing is man-made--is that it is occuring VERY quickly, compared to natural cycles. And that's the biggest problem. In a natural warming cycle, pants and animals--and thus the various ecosystems around the world--have thousands of years to adapt. This time, there's no time. And that means we are going to see not only climate change and coastal flooding, but massive ecological disruption, unless we get busy and make the changes we need to to stop global warming from getting worse.

Answer 4

People are not responsible for ALL of the warming now. They are just responsible for making it occur faster and with a higher level of heat. The previous warming trends were natural. The current warming trend is also somewhat natural, but has been greatly increased due to human actions.

Perhaps you should do a little research?

Answer 5

I do believe humans are polluting the earth, and helping global warming, but I do not think we are the full reason. Abut 20-30 years ago there was what is called the maunder minimum. It was about 11 years with very cold winters, and cool summers. This was caused by the lack of sun spots on surface of the sun. The sun works in a twisting motion, once it gets wound up, it spins the other direction. this process lasts about 22 years. 11 years spinning one way, and 11 years going back. The sun is just getting ready to unspin soon, and the earth's temperatures will drop. Maybe not too greatly, but they will.

Answer 6

obviously other causes ,
why is it relevant to what is happening now ,
is there a rule that says ,everything must always have the same causes

Would knowing that make us any less responsible for pollution .and deforestation.

And if we were less responsible would that have any effect on global warming.

What is said is that Humans contribute towards global warming that we have altered the natural
trend.

Answer 7

Global warming is, indeed, a cyclical event that goes on continuously over tens of thousands of years. The problem creating the current global warming threat is due to our Industrial Revolution of the past 150 years. Smoke-belching factories, vehicle emissions, water and air pollution, and the rape of the Earth's natural resources has escalated the natural cycle, not giving man, plants and animals sufficient time to adapt to climate changes.
-RKO- 10/19/07

Answer 8

Natural cycles, we are peaking in one now. Look at the ice core samples from Antarctica that show temperatures from current times back to 450,000 years ago. Notice that the current warming trend is not as high as the previous ones. Also notice that CO2 rises after temperature.

http://www.androidworld.com/Vostok_Ice_Core.jpg

Answer 9

Changes in the Sun.

How do we know it's not that now? Pretty simple, we measure it, and it's been going down a bit lately.

http://news.bbc.co.uk/1/hi/uk/6290228.stm

Bottom line:

"While evidence suggests fluctuations in solar activity can affect climate on Earth, and that it has done so in the past, the majority of climate scientists and astrophysicists agree that the sun is not to blame for the current and historically sudden uptick in global temperatures on Earth, which seems to be mostly a mess created by our own species."

http://www.foxnews.com/story/0,2933,258342,00.html

Great websites for more information:

http://profend.com/global-warming/
http://environment.newscientist.com/channel/earth/dn11462

Answer 10

The temperature was constant for 650 million years. It was 1980 when the temperature changed. Look at the IPCC report and Al Gore's book. It was all honky-tonky until CO2, the main driver of everything, cooked the planet.