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Has the world warmed since 1998?
Oct. 12th, 2014 09:51 pmI wrote the following in response to an online comment which claimed that there's been no global warming since 1998:
The idea that temperatures haven't risen since 1998 is flawed on multiple counts.
For one thing, 2005 and 2010 were hotter.
Second, 1998 has been cherry picked as the starting point because a "super El Niño" weather system caused more heat to be moved from the ocean to the atmosphere, causing an upward blip in temperature compared to the surrounding years. To compare like with like we would need to wait for another super El Niño year.
Third, the assertion is based on looking at the data for a start year and an end year, and ignoring all the data in between (and the data prior to the start year) – a statistically bogus technique.
Fourth, this time period is too short to give a statistically significant result – a period of 30 years is generally preferred, so we can see the long-term trend without interference from natural variability and things like the 11 year solar cycle.
Finally, and most importantly, most of the warming is going into the ocean, and when you look at ocean temperature data, there is no pause in warming. The distribution of heat between the surface and the ocean varies over time (e.g. due to weather patterns like El Niño and La Nina), and the extra heat absorbed into the ocean in recent years isn't going to stay down there forever – when the pendulum swings in the other direction, we may see quite a rapid rate of surface warming.
The idea that temperatures haven't risen since 1998 is flawed on multiple counts.
For one thing, 2005 and 2010 were hotter.
Second, 1998 has been cherry picked as the starting point because a "super El Niño" weather system caused more heat to be moved from the ocean to the atmosphere, causing an upward blip in temperature compared to the surrounding years. To compare like with like we would need to wait for another super El Niño year.
Third, the assertion is based on looking at the data for a start year and an end year, and ignoring all the data in between (and the data prior to the start year) – a statistically bogus technique.
Fourth, this time period is too short to give a statistically significant result – a period of 30 years is generally preferred, so we can see the long-term trend without interference from natural variability and things like the 11 year solar cycle.
Finally, and most importantly, most of the warming is going into the ocean, and when you look at ocean temperature data, there is no pause in warming. The distribution of heat between the surface and the ocean varies over time (e.g. due to weather patterns like El Niño and La Nina), and the extra heat absorbed into the ocean in recent years isn't going to stay down there forever – when the pendulum swings in the other direction, we may see quite a rapid rate of surface warming.
