Can you name a reputable climate scientist that denies global warming is due to increased greenhouse gases?

No. By definition this theoretical "scientist" would lose all credibility. Denying the existence of climate change and mans significant effect on it would be like denying the existence of gravity. No, its worse; denying climate change would be worse than denying the existence of gravity.

Yes, in DenialWorld, there are plenty. For example,

Lord Monckton – Deniers believe his claims of being a scientist **which deniers believe, just as an $11 dollar bill, is good enough** but has a diploma in journalism and runs a PR company. On the of the top denier scientist.

Dr Fred Singer – Deniers call him ‘The Daddy of Denial’. Denies everything from acid rain to passive smoking hazards. If the paycheque is big enough, he can even deny gravity.

Anthony Watts – The foremost expert on climate science because he is an unemployed weatherman. He is the go-to guy, with plenty of opinions and data. And has a natural unenviable talent for debunking himself.

No, I know of no reputable scientist who denies physics.

If reputable means honest, NO.

depends what you mean by reputable. WIllie Soon and Roy Spencer are denier favourites.

yes