Governments and research institutions are faking temperature measurements, to make it look like the Earth is warming.
Fact:
This claim is completely ludicrous, as it implies that the US government is part of a conspiracy, even with President Trump declaring that global warming is a hoax. If it really were easy for governments to cover up the truth, you would expect the US to have planted weapons of mass destruction in Iraq, to justify the 2003 invasion. Instead, it sent 1,500 weapons inspectors to scour the country for WMD, then admitted that no such stockpiles existed. Conspiracy theories are almost never true, particularly in countries where the government is held accountable by voters and the media. [In authoritarian regimes, by contrast, it is a different matter, as the government controls all the levers of power. Even so, the truth still has a way of getting out over time.]