Be careful. The Heartland Institute is a professional disinformation firm. Their business is to write plausible-sounding lies, then trick media outlets into publishing them.
If the Heartland Institute writes something, it's not just wrong, you can expect the reverse is true. Moreover, it also tells you that some big corporation is throwing large amount of money to ensure you are staying in the dark. In this case, ExxonMobil paid The Heartland upwards of $500'000 as part of a larger effort to delay cap-and-trade legislation in Washington.
The Heartland Institute is scary scary stuff. They rely on the fact that constructing proper counter argument takes vastly more effort than to make stuff up. If people consistently insist for proper counter-argument to their articles, they will stay ahead, and they win. It's a technique called Gish Gallop.
The scientist, Roy Spencer, has destroyed his credibility in matters of global warming, by publishing flawed results, being caught, but then nevertheless encouraging disinformation firms to use his papers for advocacy.
What if you held a conference, and no (real) scientists came?
The Heartland Institute Publishes a Bogus List of Scientist with Doubts
Naomi Oreskes talk on Merchants of Doubt: How a Handful of Scientists Obscure the Truth about Climate