They go outside, and the temperature is cool. Maybe they see a huge snowstorm on the news. Because of this, they assume the Earth can't be warming. It has to be getting colder because their world is circumscribed by what THEY can feel and see.
They have no clue that the ENTIRE Earth is taken into account and not just what is in their twee little minds.
Global warming:
There is no single thermometer measuring the global temperature. Instead, individual thermometer measurements taken every day at several thousand stations over the land areas of the world are combined with thousands more measurements of sea surface temperature taken from ships moving over the oceans to produce an estimate of global average temperature every month (see the sections on how climate is measured ).
From these records, the ten warmest years in the instrumental record of global temperature (since around 1880) all occur within the 12 year period 1997-2008. Although 2008 data below show it was the coolest since 2000 due to the moderate to strong La Niña that developed in the latter half of 2007. However, the total global temperature increase from the 1850s throught to 2005 is 0.76°C (1.36°F) and the rate of warming averaged over the last 50 years is nearly twice that for the last 100 years. So don't be lulled by one year where it is relatively cooler, what we need to look at is decadal or long term trends.
http://www.global-greenhouse-warming.com/global-temperature.htmlAs you can see, while there are cooler temperatures at times, the overall temperature arc is moving up. This is data from thousands of points and not ideas posited by bubbleheads in various places. That would be an interesting graph.