Solar, wind and hydro technologies convert enthalpy into entropy and would cool the Earth, except that it is in dynamic radiative balance with the Sun, which has a relatively infinite energy supply and would restore the equilibrium. The enthalpy has to be restored from the Sun because the enthalpy cannot be replaced, except from higher temperatures by the Second Law of Thermodynamics, ultimately by the temperature of the Sun. There would be additional warming of the Earth to maintain its temperatures, causing global warming. Therefore renewable energy would not reduce global warming. The theory that reducing fossil fuel combustion would reduce warming by carbon dioxide could be tested, as I have described in my Proposal to Demonstrate Greenhouse Warming see martinknox.com and my book Animal Farm 2 available on Amazon.
My attempt at resolving this complex matter is summarised below.
Utilisation of electrical energy extracts, converts into electricity and then wastes as heat transferred to the environment, all of the chemical enthalpy in a fossil fuel, which is not replaced because it would be conserved on Earth by the First Law of Thermodynamics, as entropy, unusable energy. For an equal quantity of electricity, from solar, wind or hydro energy, it would be converted, used and wasted in the same way, but its enthalpy would have to be replaced to restore the Earth-Sun dynamic radiative equilibrium.
To maintain on Earth systems of wind, precipitation and solar energy for renewable energy technologies, the enthalpy taken and used has to be replaced from higher temperature sources, not entropy. The Second Law of Thermodynamics, allows heat to move only from warmer systems to cooler systems. Solar, wind and hydro enthalpies taken on Earth must be restored ultimately from the Sun’s higher temperature. To argue that Earth’s climate system energy would not be affected by renewable technologies because their amount is lesser is a priori, a fallacy and unsound.
Therefore, supposing that solar, wind and hydro technologies could equal the thermal efficiency of fossil fuel technologies, the renewable technologies would bring more solar energy to the Earth. The amount of heat trapped by carbon dioxide emissions from fossil fuels could be offset by restoration of solar, wind and hydro energy taken by renewable technologies.
Further explanation is in my book Animal Farm 2 on Amazon and posted on my blog.