Often you will hear climate change deniers whine that the Earth hasn’t warmed since 1998. Just a quick look at the breaking of temperature records would seem to indicate this statement is just another denialist lie. 2005 was hotter than 1998, and 2010 was hotter than 2005, and 2014 was hotter than 2010, and 2015 was hotter than 2014, and 2016 was hotter than 2015. Indeed, in 2016, the earth’s surface was the warmest it has been since modern record-keeping began in 18801.
Globally averaged temperatures in 2016 were 0.99 degrees C warmer than the mid-20th century mean and was the third year in a row to set a new record for global average surface temperatures. Most of the warming has occurred in the last 35 years, with 16 of the 17 warmest years on record occurring since 2001. In addition, eight (January-September) of the 12 months of 2016 were the warmest on record for those respective months1.
The last time the Earth was this warm was 115,000 years ago, during the last interglacial2 and it is 4 million years ago since the earth’s atmosphere had this high a concentration of carbon dioxide in it3. While in 2016, the presence of an El Niño event4 had an effect on climate and temperature, it is estimated by the National Aeronautics and Space Administration (NASA) that 90% of the warming was due to increased levels of carbon dioxide in the atmosphere3 rather than the El Niño event.
It is also common for climate change deniers to only refer to atmospheric or surface air temperatures, presumably because they are affected by such phenomena as El Niño events. This is the denialist technique of cherry-picking; pick the data that seems to support your story. However, there are more useful indicators of the overall warming of the planet. For instance, more than 90% of the heat goes into warming the oceans, while less than 3% of the heat goes into the air temperature. Data obtained from the oceans show that this heat content has been steadily increasing and there are some indications that the rate of warming has increased5.
Figure: Heat content of Land, atmosphere and ice (orange), ocean of 0-700m depth (light blue) and ocean of 70-2000m depth (dark blue). From Nuccitelli et al. (2012)5.
So, if someone tells you that the Earth hasn’t warmed since 1998, they are simply lying, or are ignorant of the facts.