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Did global warming stop in 1998?
1998 was an unusually hot year as it featured the strongest El Nino of the century. In fact, from Jan to May, 2007 is tied with 1998 as hottest year on record. The WMO reported in August that January and April 2007 were the hottest on record.
However, when determining trends, you don't pick one month or year out of isolation - particularly if that year features a short term weather anomaly like El Nino. By this method, based on the fact that 2005 was .17°C hotter than 2000, you could conclude that the rate of global warming doubled from 2000 to 2005.
5 year moving average
When considering long term climate trends, you need to filter out short term weather anomalies like El Nino or volcanic eruptions - an easy way is to plot a 5 year average. This shows the trend hasn't reversed at all.
Line of best fit
While a 5 year average is visually compelling, a more rigorous statistical method to determine any trend is to apply a line of best fit to the data.
In this case, a line of best fit calculates the temperature trend is 0.16°C per decade from 1998 until July 2007. This is a close match to the temperature trend over the last 30 years (0.15°C from 1975 to 2007). So even starting from 1998, we find the planet is still warming at the same rate.
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