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It's the sun
Climate's changed before
There is no consensus
It's cooling
Models are unreliable
Surface temp is unreliable
Ice age predicted in the 70s
We're heading into an ice age
It hasn't warmed since 1998
Antarctica is cooling/gaining ice
View All Arguments...


Latest Posts


Skeptic of the Week

The award for most skeptic arguments in a single article over the past 7 days goes to:
The Climate Change Climate Change by The Wall Street Journal (3 arguments)

Scientific skepticism is a healthy thing. Scientists should always challenge themselves to expand their knowledge, improve their understanding and refine their theories. Yet this isn't what happens in global warming skepticism. Skeptics vigorously criticise any evidence that supports anthropogenic global warming and yet eagerly, even blindly embrace any argument, op-ed piece, blog or study that refutes global warming.

So this website gets skeptical about global warming skepticism. Do their arguments have any scientific basis? What does the peer reviewed scientific literature say?


Thursday, 18 June, 2009

The CO2/Temperature correlation over the 20th Century

Previously, we looked at the correlation between CO2 and temperature over the past 40 years. However, as I'm always saying, you need to look at the broader view, not just a single piece of the puzzle. The 40 year period was chosen to demonstrate that even during a period of long term warming, internal variability causes periods of short term cooling. What if we look at a longer time series? Over the past century, are there any periods of long term cooling and if so, what is the significance?

Read more...

Posted by John Cook at 4:28 PM   |   51 comments


Monday, 8 June, 2009

This just in - the sun affects climate

A new Daily Tech blog post is propagating through the blogosphere, claiming a new NASA study attributes recent warming to the sun. The "new research report" is a NASA press release released in May 2008. The press release mentions that "fluctuations in the solar cycle impacts Earth's global temperature by about 0.1 degree Celsius, slightly hotter during solar maximum and cooler during solar minimum". This impact of the solar cycle on climate has been known for years.

Read more...

Posted by John Cook at 7:57 AM   |   14 comments


Thursday, 4 June, 2009

The correlation between CO2 and temperature

This week, Australian TV channel ABC aired an interview with Australian senator Steve Fielding. The senator is studying both sides of the debate and genuinely seems to be struggling with the question of whether man is causing global warming. He found particularly persuasive the argument that in recent years, global temperatures have been falling while CO2 has been rising.

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Posted by John Cook at 3:34 PM   |   26 comments


Tuesday, 2 June, 2009

What causes short term changes in ocean heat?

Over the past 40 years, global ocean heat content has shown a long term warming trend. However, the warming hasn't been monotonic. There are periods where ocean heat drops for several years before the warming trend resumes. On several occasions, this is due to large volcanic eruptions which cause a drop in global temperatures. On other occasions, upper ocean heat drops with no volcanic activity. What causes these breaks in warming?

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Posted by John Cook at 9:30 AM   |   6 comments


Monday, 18 May, 2009

Does ocean cooling disprove global warming?

Last week's post on sea level rise yielded some interesting comments on ocean heat including some new papers I reference below (h/t to Chris). However, I confess my interest waned when the discussion turned to the relative merits of Energy and Environment. While the validity of editor reviewed literature versus peer review is an important issue, such topics yield no actual understanding on the latest developments with ocean heat content. So what does the science say?

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Posted by John Cook at 10:07 AM   |   39 comments


Tuesday, 12 May, 2009

A broader view of sea level rise

The last post on sea level rise emphasised that when analysing sea level rise (or any climate trends for that matter), it's inadequate to use just a few year's worth of data. However, I only went back 16 years. To obtain a more complete picture of sea level rise, I'm taking my own advice and going back to 1870.

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Posted by John Cook at 7:25 PM   |   36 comments


Thursday, 30 April, 2009

Are sea levels rising?

A common error in climate debate is drawing conclusions from narrow pieces of data while neglecting the whole picture. A good example is the recent claim that sea level rise is slowing. The data cited is satellite altimeter measurements of global mean sea level over the past 16 years (Figure 1). The 60 day smoothed average (blue line) seems to indicate sea level  peaked around the start of 2006. So one might argue that sea levels haven't risen for 3 years. Could one conclude that the long term trend in sea level rise has ended?

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Posted by John Cook at 6:47 AM   |   10 comments


Saturday, 25 April, 2009

How to cherry pick your way to Antarctic land ice gain

I've been reflecting on the recent poll that found a record 41% of people now think global warming is exaggerated. Meanwhile, 86% of climate scientists think we won't restrict warming to under 2°C. Why the discrepancy between qualified climate scientists and the general public? I would suggest that scientists are not always completely effective at communicating their science to the average person. Global warming skeptics, on the other hand, have a wide range of rhetorical techniques that are quite successful in sowing doubt.

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Posted by John Cook at 12:33 AM   |   18 comments


Monday, 20 April, 2009

Is the climate warming or cooling?

The most popular skeptic argument in recent times is that global warming has stopped and we're now experiencing global cooling. For example, if we fit a linear trend line to global temperature from 1998 to 2008, we find no statistically significant trend. However, if we fit a trend line from 1999 to 2008, we do find a strong warming trend. It's all too easy to cherry pick start and end dates to reinforce whatever point of view you wish to promote. But what is the most appropriate way to view temperature data?

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Posted by John Cook at 7:47 PM   |   36 comments


Thursday, 2 April, 2009

Why is Antarctic sea ice increasing?

While Arctic sea ice loss has shown dramatic decline over the past few decades, Antarctic sea ice has shown long term growth since satellites began measurements in 1979. This is an observation that has been often cited by skeptics as proof against global warming. However, in all the skeptic articles I've read, not one has raised the crucial question: why is Antarctic sea ice increasing?

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Posted by John Cook at 6:43 AM   |   31 comments

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