Disagreement on the issue of climate change was anticipated from the beginning of the meeting in Hamburg and Germany Chancellor Angela Merkel has expressed that is “the one crucial issue” to be discussed at the meeting. The US broke with the other members of G20 in June when it abandoned a coalition of 147 nations in the Paris Climate Accord. At the time, Trump insisted that the agreement would be renegotiated but other leaders said that was a pipe dream. Chancellor Merkel reiterated in Hamburg that “the other 19 member states of the G20 say that the Paris agreement is irreversible.” She also made it clear that she “deplores” the fact that the US pulled out of the accord.
Details about the mechanism of a Lofstrom loop can be found here