Why is climate change caused by humans?

Answer 1

• Scientists know that the earth is kept warm through the greenhouse effect.
• They know that greenhouse gases absorb infrared heat.
• They know that carbon dioxide is a greenhouse gas.
• They know that burning fossil fuels releases carbon dioxide that has been hidden away for 300 thousand years.
• They know that levels of carbon dioxide in the atmosphere have been rising since the Industrial Revolution, when man started seriously burning fossil fuels.
• They know that forests, through the process of photosynthesis, remove large amounts of carbon dioxide from the air.
• They also agree that man has been cutting down the forests of the world so that this huge carbon sink is just a fraction of what it was.
• So they know that global warming is being caused by human activity.

Answer 2

I have looked at the scientific evidence. I can see that official reords show a rise in average global temperatures since the beginning of the Industrial Age, and that the rise has accelerated since the late 1970s, coinciding with expanded industrial activity. I have followed the scientific debate that confirms the reliability of the official readings, and find this evidence far more reliable than the non-expert claims global warming is not happening or that it is not of recent origin. I understand the science that says that greenhouse gases such as carbon dioxide can cause global warming. I have examined summaries of the evidence that shows that most of the quite substantial increase in atmospheric concentrations of carbon dioxide must come from the burning of fossil fuels, and therefore from human activities. I therefore believe that I know we humans are causing global warming.

Answer 3

Because there is a link between global warming and rising greenhouse gas concentrations. And there is a link between rising greenhouse gas concentrations and human activity. Concentrations of greenhouse gases such as CO2 started to rise during the industrial revolution, when humans started to use more and more energy.

The link between greenhouse gas concentration and human emissions of greenhouse gasses is, in fact, firmly established. Scientists have looked at the isotope ratios of the CO2 in the atmosphere and determined that the increase in atmospheric CO2 can only be coming from the burning of fossil fuels. Cause and effect, in this case, are established.

Answer 4

Humans are accepting the blame for global warming because the evidence is that we are causing it. There is no point in being in denial when the facts are there. What is far more important is that we also take the credit for fixing the problem before it is too late.

One reason is that humans pump 40 billion tons of additional CO2 into the atmosphere each year. Carbon dioxide is a heat trapping gas.

Another reason is that every other potential cause for global warming of which we could conceive has been examined and rejected as a primary cause. The sun's output has been carefully measured and is not increasing. There is no significant measurable difference in cosmic ray bombardment. Earth's natural orbital cycles (Milankovitch Cycles) indicate earth should actually be gradually cooling now instead of heating up. No other known natural cycle explains the measured global temperature gains. The increase in heat trapping gas, however, DOES explain it, quite well.

Answer 5

Temperature readings taken from around the world since 1850 prove that the global average temperature has risen by around 0.75 degrees Celsius, so there is no question that there has been a rise in average global temperatures coinciding with industrial activities.

Scientists proved in the nineteenth century that greenhouse gases are responsible for keeping the world some 30 degrees Celsius warmer than it otherwise would be. In 1896, Arrhenius completed a laborious numerical computation which suggested that cutting the amount of carbon dioxide (CO2) in the atmosphere by half could lower the temperature in Europe some 4-5°C (roughly 7-9°F) - that is, to an ice age level. Arrhenius made a calculation for doubling the CO2 in the atmosphere, and estimated it would raise the Earth's temperature some 5-6°C (averaged over all zones of latitude). His calculations did not take into account the effect of the oceans in ameliorating the effect of rising carbon dioxide levels, and in any case Arrhenius and other researchers were only interested in explaining the Ice Ages. No scientist at the time seriously believed that global warming was coming, but they had demonstrated that changes in carbon dioxide levels would cause global warming.

However, chemical analysis of the atmosphere has since shown that atmospheric CO2 concentrations have increased by some 35 per cent since the beginning of the Industrial Age, from the long-term average of 260-280 parts per million (PPM) to the present level of 380 PPM. Scientists say that by burning fossil fuels, we are now releasing nearly 30 billion metric tons of carbon dioxide annually, in addition to the emissions caused by cement manufacture and deforestation. Analysis of the proportions of atmospheric carbon isotopes C12, C13 and C14 also proves that most of the increased levels of atmospheric CO2 do come from fossil fuels.

This evidence shows that increased atmospheric carbon dioxide concentrations would cause global warming, and that the observed increase has resulted from human activities. Most climate scientists therefore believe that human activities have been a significant factor in causing global warming and consequent climate change.

Answer 6

A lot of people believe humans are causing global warming because it is a true issue .. caused by people. We really are causing global warming, when we pollute and waste the earth dies just a bit, and with everyone on this glorious planet god has given us it really does build up.

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The fact is that we simply do not know if man is a significant contributor to global warming, or if he is aiding it at all.

Answer 7

Climate change is not necessarily caused by humans. Climate change can and would occur even without human influence. Solar cycles will affect global temperature averages; the precession of the Earth's rotational axis will cause climatological cycles; geological processes such as continental drift and volcanism will affect global climates.

However, humans do influence climate, primarily through our contributions to the envelope of greenhouse gases present in our atmosphere. We know this because, even if we eliminate all other known factors, such as the ones mentioned above, we're still stuck with an offset in global warming that can only be accounted for by human influences.