If you mean adjusting past temperatures downward to show more warming, manipulating data, deleting cooler weather stations to show warming, etc... then yes, human activity is the major contributor.
No, actually I meant the clear cutting of most of the boreal forest, the temperate rain forest and the tropical rain forest. Also the forests in Pakistan... note the flooding, the mid-east that didn't use to be entirely desert, the great plains and prairies that wouldn't have turned into dust-bowls in the 20's if it wasn't for agriculture. The near extinction of the bison, the extinction of the carrier pigeons, the near extinction of the many of the west coast wild salmon runs, the extinction of some of those runs, the dumping of the mega-tonnes of green-house gases into the atmosphere, the dumping of hormone altering pollutants into the water.... etc etc etc
And if you want to know which bit of the climate changed (notice I didn't say 'warming') by the extinction of the carrier pigeons.... well, we'll never know... but there was a small, localized, change to the local environment in the foothills of the American Rockies when the ranchers extirpated the wolves. Thankfully the Canadians didn't, and now things are getting back to 'normal' in the foothills with some imports. Wonder if they needed visas?
Humans are arguably making the climate 'warmer'... I do believe that. But there is not much argument that humans do more to 'change' the climate, whether cooler or warmer, in everything they do.
[When the wolves were eliminated, the deer population exploded, and they ate the aspen shoots that grow along the streams, never becoming adult trees that protected the streams from summer heat and evaporation. When the streams dried up the ponds and lakes downstream also dried up. All the natural grasses and vegetation that grew along the streams and ponds and lakes also dried up and died, making the area hotter and drier. And dustier. Climate change (localized) because the wolves did what wolves do - they predated sick and weak cows and the ranchers wanted to sell those cattle so they shot the wolves.]
