How much of the recent warming has been caused by humans?

Question

I would like to see arguments regarding how much of the warming over the past 100, 50, and/or 30 years has been caused by humans, and how much has been caused by other factors.

Please provide evidence to support your argument. Answers which do not provide supporting evidence will not be answering my question, and thus will be violating the community guidelines and will be reported.

Answer 1

I' ve created this graph which shows how the temperature of the planet has changed over the last 100 years... http://profend.com/temporary/image3377.gif It applies a 10 year central moving average to the two most frequently cited temperature records - HADCRut3 and GISTemp.

A quick explanation of the graph. The red, green and blue lines respectively show the temperatures as per CRU, GISS and the average of both, the narrow lines show the trend over the 100 years and the up and down lines are the annual readings.

The 0.2°C difference between the two is because CRU uses land and sea surface readings, GISS just uses land.

The graph can be split into 4...

1) Warming up to approx 1940. This was mainly caused by natural events - the cycles that both the Sun and Earth go through that can affect our climate. There was an underlying human factor as well.

2) Cooling in the 40's. The natural cycles are having little effect, there's still an underlying warming trend caused by humans but the primary driver of temp change are the gases / black particulate matter that are rapidly accumulating in the atmopshere as pollution from industry and homes. This was a time before the Clean Air Acts and no-one thought twice about air pollution. As a result the atmopshere became thick with soot which blocked out sunlight and in addition there was a massive build up of sulphur dioxide, largely from power stations. This gas relfects sunlight back into space before it reaches us. This cooling effect is sometimes called 'global dimming'.

3) The 1950's, 60's and 70's. The human contribution is growing considerably but the warming effect is cancelled out by global dimming. As more Clean Air Acts are passed the atmopshere is cleaned up and global dimming slows. For much of the time natural forcings are causing a slight warming but this is overshadowed by the dimming. In the 60's natural forcings contribute to cooling, iof it weren't for this then the present warming trend would have started about 10 years earlier.

4) The 1980's onwards. Global dimming is all but a thing of the past and the atmopshere is free of soot, sulphur dioxide and some other pollutants. Early on in this period there's a slight natural warming trend but it's the human component which is by far the largest. From the 90's onwards the natural contribution has been one of cooling and despite this, temps are rising faster than ever.

Professor David Archer has put together some interesting graphs which show the natural and human components of changing temperatures over the last 150 years. This page http://profend.com/temporary/archer002.jpg has three graphs showing how the temerature would have changed if only natural or human forcings were involved. The third graph combines the two and this very closely matches the instrumental temperature record, it clearly illustrated just how our activities have affected the climate.

The second graph here http://profend.com/temporary/archer001.jpg looks back at the last 1000 years, it nicely illustrates how factors such as the sun and aerosols (particles in the atmopshere such as soot, dust etc) have remained more or less constant whereas the greenhouse gas forcing has risen sharply in the last 200 years.

TO SUMMARISE:

When all factors are taken into account then almost all the warming in the last 30 years is caused by humans (naturally there has been a small contribution). Over the last 50 years all the warming can be blamed on humans as the natural component has declined slightly. Over the last 100 years it is again down to humans, although there has been naturally induced warming and cooling, over the 100 years they're more or less in balance.

Answer 2

Greenhouse gases warm the planet, that is indesputable. The two great " snow-ball Earth" events a few millions years ago in which the ice sheets extended all the way to the equator were likely ended by carbon dioxide emissions from volcanoes.

However, considering the fact the last few decades have seen extremely strong sun-spot cycles, it can be argued much of the warming is caused by the sun. I'd assume this why the warming keeps accelerating beyond what the computer models predicted. I don't think anyone really agrees, but if you look at all the evidence from paleo-climatology and modern day meteorology, I'd say the safest bet is the warming is 70% human-caused and around 30% caused by other natural factors, mainly the sun.

Answer 3

You are making the assumption that CO2 is the driving force of so called global warming? The recent small temperature declines that don't follow the CO2 continued rise seems to have shaken some scientists from their support position.

Here is another viewpoint from:
http://www.amlibpub.com/essays/ipcc-global-warming-report.html
"Furthermore, of the tiny percentage that CO2 contributes to the greenhouse effect, 97 percent of that is due to nature, not man. Termites, for example, produce CO2 emissions many times that of all the factories and automobiles in the world. (See Science, Nov. 5, 1982.) Combining the factors of water vapor and nature's production of CO2, we see that 99.9 percent of any greenhouse effect has nothing to do with carbon dioxide emissions from human activity. So how much effect could regulating the tiny remainder have upon world climate?"

Maybe 5% looks totally the opposite of the skewed data from
the Socialist based United Nations or the Nobel prize organization that seems to have an agenda for control over the whole world.

The most likely reason for the increase in CO2 is increasing volcanic activity - remember that even the ancient Yellowstone is still venting (adding CO2). Plus 60 active volcanoes this year and UNKNOWN sub oceanic volcanoes (which covers 3/4ths of the earth) ALL ACCUMULATE over time.

Answer 4

If scientists found out what grew to become into inflicting an strangely severe style of folk to advance a definite maximum cancers, i might view that as an outstanding step in battling/curing the ailment. If scientists knew not something and the main cancers grew to become into in basic terms something "organic", to me it is the plenty scarier subject. of course, human beings might say the 1st subject is scarier in political/financial words, by using fact the main cancers's reason grew to become into desperate to be on the subject of the processing of a important nutrition source and now the government desires to tax/ban this actual production technique, which might of course harm earnings for this actual organisation. it is then related to socialism/communism/fascism, that's in turn deemed scarier than something conceivable.

Answer 5

0% of it is. Common sense will tell you that since the earth's temperature has changed many times in the past without human casueing it that the same thing is going one now. This is just the planet's natural cycle.

Answer 6

Check the data about the eruption of Mount St. Helens. You will discover that it release thousands of times the "greenhouse gasses" than man has produced in our entire history. Then multiply that number by the amount of active volcanos in the last 10,000 years. I think it will make us seem somewhat insignificant.

Answer 7

Listen to Jim Hansen on the topic at http://www.tucradio.org/new.html

Dr. James Hansen
THE THREAT TO THE PLANET
How can we avoid dangerous human-made climate change
Dr. James Hansen is one of the few scientists who have consistently warned that the impact that humans have on the climate is bringing about changes that are faster than we ever believed and may be irreversible if action is not taken now. Hansen is Director of the NASA Institute for Space Studies in New York City, and he teaches at Columbia. Since the late 1970s, he has worked on studies of the Earth's climate. He has run afoul of government censors since the 1980s. Repeatedly his testimony before Congress was suppressed or re-written.

Hansen says that the unprecedented and rising amounts of greenhouse gases added each year AND the speed at which we are altering the energy balance of the earth are completely out of the range of proven earth history of hundreds of thousands of years. Hansen fears that we may soon be reaching feedback mechanism or tipping points such as the melting of the ice sheets that has already begun on Greenland and West Antarctica.


In part one of this program Hansen gives a fascinating account of the earth's climate history, in part two he talks about solutions. Dr. Hansen's work - including the slide projections for this talk, can be found at < http://www.columbia.edu/~jeh1>
For a broadcast quality mp3 version of Part ONE click HERE
For a broadcast quality mp3 version of Part TWO click HERE
For a PODCAST of Part ONE click HERE
For a PODCAST of Part TWO click HERE

Hansen will tell your the conclusions are based on the compositional and isotopic analysis of the tiny bubbles of gases from ancient atmospheres enclosed in ice core samples (columns or tubes of ice going back 400,000 yrs). The ice cores were obtained by drilling down through the ice of glaciers located in Greenland and Antarctica. The mountaintop glaciers have also been sampled ,like Kenya's Mount Kilimanjaro, and that data from those places backs up and confirms the data from Greenland and Antarctica.

The demagogues who claim GW evidence is fiction are for the most part people who quote as sources scientists paid by the industries who want to maintain the status quo as long as there is profit to be made selling fuels from fossil carbon fuels made from petroleum and coal. These energy sources are finite and eventually will run out. But as of right now, demand is beginning to outstrip existing reserves. That's why you see the incremental barrel of oil of 42 gallons priced at 100$/BBL. That price is telling us this: The reserves left to be found are marginal oil and coal fields and will not be brought to market fast enough to keep energy costs stable much less reduce them. The coal and oil industries know this but they, bottomline, only serve the interests of their investors(that the mantra of all megacorporations who rarely do more than pay lip service to social responsibilities we in as individual have. These corps do things only went given tax credits at taxpayer's expense. What's this to do with GW, you say? The changes that need to be made will not come fast enough from for-profit corporations making money selling and using coal and oil, and it must be the get, the people's government who compels them. and everyone else in the fossil fuel consumption chain including us "addicted-to-oil-&- cars" consumers, to do the right things to slow and reverse adverse global changes due to GW. Soon before we all turn this planet against us! I really wish people would listen to the experts who care about the truth and not personal profit.

Keep the faith ! Stay the course ! The scientific facts are against the amoral ne'er-do-wells disputing the reality of the GW problem, much as incompetent oil industry backer BUSH43 did for the last 7 years, posting misinformation in the environment categories.

(((This is not a personal attack on their person but on their positions and comments -and if reported and deleted will only let us know that YA is not committed to free speech and the concept of truth. I say this because I have seen Q's and A's on the subject of GW deleted when they should not have been. All who read this A should check back to verify its continued existence. And support by other A's agreeing with me would be appreciated.)))

It takes alot of effort to post these coherent and relevant A's to good Q's and I dislike, no hate ,seeing them censored by YAT deletion. Speaking truth to power matters more than the gaming features of the Q&A service provided by YAHOO who is supposed to be one of the good guys since they helped make the net better for individuals like me. I wonder if they still have that commitment? I know AOL doesn't and never did which is why they are dead to me. Yahoo does need to straighten up their act based on recent news articles. Or more people will be turning elsewhere.

Re this volcanic activity point:

"0% of it is. Common sense will tell you that since the earth's temperature has changed many times in the past without human casueing it that the same thing is going one now. This is just the planet's natural cycle."

Hansen's Data makes your point absurd since the historical record derived from ice core samples takes your volcano data into consideration.

Please leave climate science to the climate scientists who have been studying the issue for a lifetime!

Untrained , inexperienced common sense is BS! and easily refuted by scientifically trained & informed research minds from MIT-Harvard quality Schools. Rice is one of them.

Answer 8

0% unless you believe the propaganda of the enviromentalist wackos.