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This website

Climate change global temperature from a governmental organization, shows 2 graphs , one called "History of global surface temperature since 1880" and the other called "Yearly surface temperature compared to average (1850-2018)" which seems to show global temperature dropped the last 2 years. The second graph shows as source NOAA, NASA, University of East Anglia and the Japan Meteorological Agency. The lines of all of them are going down for the last 2 years.

But for NASA in particular, you have in their official website Global temperature a graph called "GLOBAL LAND-OCEAN TEMPERATURE INDEX" which measures "temperature anomaly", which shows for the 2 years the temperature going up.

My question is, and even more considering both websites share one of their sources,

Did global temperature increase or drop in the last 2 years?

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  • $\begingroup$ That NASA site is showing me 2016=+0.98, 2017=+0.9, 2018=+0.82 for the index, so consistent with the NOAA site. Are you getting something different? $\endgroup$ – Deditos Sep 22 at 21:38
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Did global temperature increase or drop in the last 2 years?

Before I answer the question, I need to add the caveat that climate change does not say that every year will be warmer than the previous one. Events such as El Ninos and La Ninas can make the global temperature spike or drop in any one year. The Pacific Ocean dumps huge amounts of pent up heat into the atmosphere during El Nino events.

2014 saw the start of an El Nino event that briefly stalled but then became one of the largest such events ever observed. The 2014-2016 El Nino made 2015 and 2016 the warmest years on record -- so far. 2017 and 2018 were a bit cooler than 2015 and 2016. They were however warmer than every year on record prior to 2015.

2019 most likely will not be warmer than 2016, but it might well beat 2015 as the second warmest year on record. And that is without the help of a massive El Nino event.

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First we should be clear on what is meant by "global temperature". Averaged global surface air temperatures have become the most commonly used metric for the state of our global climate and get called "global temperature" but it is not an absolute measure, is not a direct measure of global climate change and it is not the only measurement that could be used. It does have the advantage of drawing on temperature records going back to before 1900. Surface air temperatures are only a good indicator of climate change when averaged over periods long enough that short term and recurring variability does not distort any calculation of trend.

This graph shows an ongoing pattern of temperatures going up and down a lot - whilst still showing a longer term trend of temperature rise.

enter image description here

Average surface air temperatures vary widely from year to year - and yes, they have gone down 2 years running. Before that they went up for 5 years in a row. However this does not mean that there was global warming for 5 years and global cooling for 2 years; a clear underlying trend of warming (red line is smoothed 5 year running average) is there, and if anything it is shows faster warming, not slower.

Looking at a different measurement - This is global ocean heat content down to 2,000m depth - it shows year to year variation but much less. It does not show 5 years of Ocean heat content going up followed by 2 years of going down or even align closely with the variations in surface air temperatures but the same underlying trend of warming as in surface air temperatures is there -

OHC2000m

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