Tuesday, 9 February 2010

Truth or Lies

Too many politicised blogs take positions on global warming, referring to scientific studies and purporting to be fair and unbiased, but clearly having an agenda. At Carbon Clear, we try to help companies make informed decisions about how to respond to climate change.  But that requires sound data.

I’ve been reminded of the classic book by Darrell Huff How to Lie with Statistics, first published in 1954 and now as relevant as ever.  
Sometimes intentional, sometimes inadvertent, it’s not hard to arrive at erroneous or misleading conclusions using data inappropriately and misrepresenting reality.  Moreover, depending on your inherent biases and interests, you can construct the world as you like it by picking and choosing data points to support your worldview.  Take global mean temps over the past 20 years based on NASA’s Global Land Ocean Temperature Index.  Using this table, and selectively choosing data points, I can make two conflicting statements about climate change, both of which are true.
  • Annual global mean temps 1990 to 1996 dropped by almost 1%.
  • Annual global mean temps rose from 1989 to 1998 by about 2%.
So a reality check for these statements is needed.  Are these time periods relevant? Are the data points (i.e. years chosen) representative of long-term trends?   The short answer to these questions is no and no.   Changes in global mean temps over short time periods are unlikely to reveal anything significant in climate change science given the temperature amplifying effects of El Nino or the countervailing cooling effects of volcanoes.   So let’s let the scientists do the science and interpret the data – we have a large enough role trying to communicate clearly climate change issues.  And while we ask questions, let’s try and ensure that the science is not misused or abused.