Well, the experts have been wrong more than 50 times on climate changes in the past century, so I will take with a large bowl of salt, any government funded experts guesses. When they move most of those sites where they are measuring to an area that doesn't have compromised data due to city environment of asphalt and cement, they will become more believable. Take a look at the summer temperatures in 1926 of the continental USA.
The same question you asked about where information is coming from can be asked of your saying "...Well, the experts have been wrong more than 50 times on climate changes in the past century,...".
In 1926 the world's population was 2 billion... Today it's almost four times that at 7.8 billion... This means a relative increase in "...city environment of asphalt and cement..." throughout the world.
Additionally, the Industrial Revolution which began around 1760 was only 166 years into its development related to the production of products for a 770-million world population and its increase of 2 billion (an almost 160% increase). Over the following almost 100 years, the increase in the population that the manufacturing industry serves has risen by almost 290%.
That's a possible 290% increase in "...city environment of asphalt and cement..." throughout the world since 1926.
Your own words, bob, kind of undermine the point you're trying to stand on.
The world situation today is most certainly not what it was back in 1926. And it's not just today versus almost a hundred years ago... It is the accumulated impact of what has been taking place over these almost 100 years... The Great Pacific Garbage Patch wasn't created yesterday. And the massive amount of human refuse that has been dumped in the sea, and on land, didn't happen yesterday either.
Now I'm not a climate change shill... But I certainly don't have my head buried in the sand... Climate changes are taking place for very specific, identifiable reasons... And these changes are not going away tomorrow... Just as surely as the world's population growth and all the "...city environment of asphalt and cement..." growth isn't going away tomorrow either.
Unfortunately... The truth of the matter is... "...Houston, we've have a problem here...".