• Question: Do you think that humans are responsible for causing Global Warming?

    Asked by scienceiscool to Cathal, Ciara, Emma, Michael, Sive on 14 Nov 2013.
    • Photo: Sive Finlay

      Sive Finlay answered on 14 Nov 2013:

      Hi,

      Great question! Humans are probably not the only cause of global warming but we’re definitely one of the major contributing factors.
      The Earth’s climate has changed many times in our planet’s history. The axis on which the planet rotates shifts very slightly over millions of years which means that sometimes parts of the Earth are tilted slightly closer or further away from the sun. The Earth’s climate has gone through cycles of warming and cooling for millions of years.
      So global warming is not a new thing; it might have been one of the causes of the mass extinction of dinosaurs 65 million years ago, long before humans were around.
      What’s clear, however, is that human activity has accelerated the effects of global warming far beyond the “natural” cycles of climate change. There’s lots of evidence that human activity, particularly in the last 150 years, has caused increased levels of greenhouse gas emissions into the atmosphere and that average global temperatures are increasing. Although of course the greenhouse effect doesn’t just produce warming; some places are getting cooler and weather patterns in general are more variable and unpredictable. There’s a very famous graph from a long-term study in Hawaii which shows how rapidly atmospheric carbon dioxide levels have increased in the past 50 years; a trend which is undoubtedly a result of human activity http://www.esrl.noaa.gov/gmd/ccgg/trends/#mlo_full
      So I think global warming is a natural part of climatic cycles on our planet but humans are responsible for a rapid increase in global warming over a relatively short space of time which means that most species can’t adapt quick enough to keep up with the changes.
      Sive

    • Photo: Michael Nolan

      Michael Nolan answered on 18 Nov 2013:

      Hi there,

      super question.
      The earth continually cycles through significant climate change with average temperature changes of a few degrees either way. This usually take places over many millenia and so the ecosystem of the planet has time to adapt to these changes.
      It is clear that average temperatures are growing since the dawn of the industrial revolution and the amount of CO2 spewed into the atmosphere is also growing extermely quickly. Some of this could be natural as we go through a cycle, but the pace of the change is much faster than would occur naturally and this is the key point.

      By pumping 30 Gigatons of CO2 into the atmosphere each year, the concentration of CO2 is trapping heat and increasing average worldwide temperatures extremely quickly. We are therefore modifying global climate (its not only glabal warming, but global climate change) very quickly and far more quickly than the earth’s ecosystem would be used to. since we have added so much CO2, the conclusion is that we are responsible for the very fast pace of change in climate (remember that on the timescale of the earth’s age, 4.5 billion years, a few hundred years is not even a blink of the eye)

      So when something like sea level rise happens, which it will, it will happen over a much shorter timespan than normal, wiping out many great coastal cities.

      The problem is that the CO2 that is there takes a long time to remove, couple of hundred years, so even if we removed all CO2 emissions today, we will still have to face the effects of the CO2 we have already accumulated over the last 250 years or so.

      Hopefully future governments and scientists will be able to work together on this problem…

      M

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