Have we passed peak oil? Photograph: David McNew/Getty images

Oil has been the world’s fossil fuel of choice since the late 1960s and our taste for it doesn’t seem likely to diminish in the short term. Oil companies are still keen to secure any undiscovered reserves while continuing to be a powerful lobbying presence.

You may think that with pressing concerns over peak oil and global warming, the world would be slowly weaning itself off the energy-rich liquid. But in the 28-year span covered by the BP data below, worldwide reserves fell only twice – in 1998, and a decade later in 2008.

Opec nations control the lion’s share, with 76% of the world’s reserves. Interestingly, many of the Opec countries’ proven reserves have barely changed in the past 20 years, despite massive exporting activity.

The largest percentage growth in oil wealth is in Vietnam, with a 39% surge in its proven oil reserves from 2007-08. This newfound wealth corresponds to 1.3bn barrels, which may sound like a lot, but would feed the world demand for less than three weeks (17 days) at 2008 levels of consumption.

Hey now, why not simply clarify some questions and try and see the whole picture? Photograph: Corbis

Is Ian Plimer ever going to answer my questions?

As some of your will be aware, I have been engaged in a bit of argy-bargy with the Australian geologist since the beginning of July.

After I criticised some of his crazy statements about climate change, he challenged me to a public debate. After some consideration I agreed, as long as he accepted my challenge: to answer some simple questions about the claims in his book Heaven and Earth.

At first he refused, then, after I wrote an article accusing him of cowardice, he accepted, and said he would address my questions and send me some of his own “after undergraduate lectures have finished today”. This was on Friday 7 August. But no answers came. Instead, on 10 August, he sent me a series of questions he had devised. They were a bizarre collection, which seem to have been designed not to be answered – and, of course, to divert attention from the fact that he wasn’t answering mine. As a couple of commenters on the thread pointed out, he appeared to be using the Chewbacca defence.