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Carbon Brief Staff

Carbon Brief Staff

03.09.2013 | 12:30pm
ScienceDangerous climate change at anything but two degrees
SCIENCE | September 3. 2013. 12:30
Dangerous climate change at anything but two degrees

While lots of people say climate change could be a serious problem, our polling shows not many think it becomes dangerous with two degrees of warming. In fact, while the answers varied significantly, they were likely to be something other than the two-degree mark.  We take a closer look.

Dangerous temperature rise

Last month, we blogged the results of a Carbon Brief/Opinium poll aiming to gauge people’s views on climate change. One set of answers stood out: the degree of warming the world would have to reach for climate change to become dangerous.

We reported that the average mean temperature respondents suggested was eight degrees celsius. That’s considerably higher than the claim often cited by NGOs, journalists, thinktanks and politicians that climate change will become much more dangerous once temperatures rise two degrees above industrial levels.

But the mean can be a blunt instrument for gauging people’s opinion as it can be skewed by some very high or very low responses.

Looking at other types of averages such as the middle answer (the median) and the most frequent answer (the mode) gives a different impression.

Our question asked people to enter a number between zero and 30. Here’s how it appeared on the survey:

temp rise poll, poll Q

As it turned out, we ended up with quite a few 30s, while most people put an answer 10 degrees or lower, and a substantial number said they didn’t know – as this graph shows:

temp rise poll, full range

While the mean temperature respondents suggested was eight degrees, the middle answer for all respondents – and the vast majority of each group – was five degrees. That’s still higher than two degrees, but not as startlingly different as the mean suggests.

This still doesn’t tell the whole story, however. A closer look at who says what reveals a more complex situation.

Women don’t mind it hotter

For example, the most popular answer for women was 10 degrees (followed by 5 degrees, then two degrees), while for men it was five degrees, with two degrees being the second most popular response. The graph below shows the range of answers by men and women:

temp rise poll, gender

Climate change causes

The answers also changed depending on people’s views of the causes of climate change.

The middle answer for people who believed climate change was happening and mostly caused by humans is five degrees, the same as for those who believed it is caused mostly by natural processes.

Interestingly, the median for those who don’t believe it is happening at all is eight degrees, with only one per cent of the group writing ‘zero degrees’.

temp rise poll, happening or not

Most of the respondents that don’t believe climate change is happening said they ‘didn’t know’ how much temperature rise would make climate change dangerous. The most frequent answer for each of the groups was five degrees… again.

It’s hard to say whether this finding is representative of the groups, however. If less than 50 people answer for a particular option it’s worth being careful about how significant the result is.

The ‘not happening’ group only contains 146 people, of which 64 entered a number, and a maximum of 16 people agreed on any one temperature rise. So the results need to be handled with caution.

So while there is some difference between each groups’ answer, a closer look shows the perils of overstating particular breakdowns.

Not two degrees

The question was a bit of an experiment, and ultimately it’s hard to draw firm conclusions about how much warming people think will lead to dangerous climate change from the results.

Policymakers themselves are dubious about the two degree mark’s scientific basis – and many scientists would argue climate change will start to become very uncomfortable well before we reach that point. But many see it is a useful way of communicating the point at which action becomes necessary.

Lots of people – about 40 per cent – chose to tick the ‘don’t know’ box rather than picking a number, with less than two per cent entering two degrees, however. So one thing we can be pretty confident about is regardless of who answers, they’re unlikely to say dangerous climate change occurs when the temperature rises by two degrees.


Our polling data is available here. Why not give it a look and tell us what you find...

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