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Would global warming happen anyway without human interference?

Would global warming happen anyway without human interference?
Kirsty J from Somerset (Aged 5-14)

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3 Responses

  1. The global climate have been changing abruptly in clycles since at leat 400,000 years ago. This cycles involve long periods (of around 100,000 years) of cold weather called as Glaciatons, wich are followed by shorter periods (around 40,000 years) of warm conditions called as Interglacial.
    Currently we are experiencing a Interglacial period that started 12,500 years ago. It means that we are living in a period in wich happen normal warming. Nevertheless, comparing the records of temperatures of the previous interglacials, we can notice that the warming in the current interglacial has occurred in a accelerated way. This process is directly related with the human activity in the world, and the damage that we cause mainly by releasing greenhouse gases and generating deforestation, among other activities not suitable for our environment. The consequences of this is the fast increase in global temperature, generating important changes in the weather, decrease in the biodiversity around the world and several other devastations.
    None of these damages would happened if human had not generated the activities that cause it, and at this time we would be experiencing a natural warming related with the present interglacial.

  2. Hi Kirsty,

    This is a tricky question, and I’m answering it because my work deals with periods of time much longer than human history: thousands or millions or even billions of years. We know that over the lifetime of the Earth (about 4.5 billion years), the climate has changed by large amounts: sometimes much hotter than now, sometimes much colder. So the easy answer is that global warming or cooling has happened before humans evolved, and will carry on in the future no matter what we do – we’re not the only reason the climate changes.

    But – and this is a big but – the world’s temperature has never changed so quickly as it is changing now, and we have lots of evidence that it’s mainly our fault, because of gases we are adding to the atmosphere. It’s the speed of the warming that is worrying, because the Earth will not be able to adapt to such a quick change.

    Temperature changes on lots of different timescales: the Earth gets hotter and then colder again in regular cycles because of how the Earth moves round the sun, and also changes for other reasons that we don’t really understand yet. So, fifteen thousand years ago it was so cold that most of Britain was covered in a huge ice sheet, and our climate has warmed up a lot since then. Over shorter periods, the temperature still changes, but not so much: for instance, between 1600 and 1800 it was cold enough to freeze the River Thames over in winter, but in medieval times before 1500 the climate was warmer. Even since 1900, we have measured periods of warming and cooling. On the (relatively) short timescales of human life, therefore, it is very difficult to predict whether the climate would naturally cool or warm without our interference.

    So my main answer is: yes, global warming might happen without human interference, but if it did, it would be a much slower change than it is at the moment.

  3. There are a number of gases (greenhouse gases) in our atmosphere which have the effect of keeping the temperature at the surface reasonably warm. Without these gases the temperature on earth would be far too cold to sustain life as we know it. The problem is that as a result of human activities the proportion of these greenhouse gases in the atmosphere is increasing, causing global temperatures to rise. When people talk about global warming they should really talk about anthropogenic, or man-made global warming, to distinguish it from the natural global warming which keeps us all alive.

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