It’s going to be a big day for Bill Gates.

Not only has the Microsoft co-founder, whose personal wealth is estimated at $US79.2 billion, committed a large piece of his fortune to a clean energy initiative on the first day of the UN climate change summit, he may also have invested in a birthday cake for his father, William H. Gates, Sr, who is turning 90.

Gates marked his dad’s 90th birthday with a touching message on his gatesnotes blog.

• Riot police clash with climate protestors in Paris
• Gates warns of robot rise
• These are the 10 richest Americans in the world

“Tomorrow is a very special day for our family – my dad’s 90th birthday,” he wrote.

“My dad has had an enormous influence on my life. He is the wisest person I know. Like a lot of sons and daughters, I didn’t always recognize my father’s wisdom when I was growing up. But eventually I figured it out and I have turned to him for advice more times than I can count.

“(He) is also one of the most generous and kind people I know. Our foundation would not be what it is without his guidance and inspiration.”

Gates concluded the message by thanking his father for “all your love”.

“I am lucky and proud to be your son.”

Clean Tech Initiative

With all eyes on the Paris climate change talks, Mr Gates is readying to launch a multi-billion-dollar clean technology initiative with a group of developed and developing countries at the UN climate change summit.

The initiative requires participating countries to commit to doubling their clean energy technology research and development budgets by 2020, and will encourage private investors to boost investment in the clean energy sector.

Australia, India, the United States, France and Indonesia are among the countries that have reportedly said they would join.

Gates will join Indian Prime Minister Narendra Modi, US President Barack Obama and French President Francois Hollande to announce the initiative on the opening day of the UN Conference of the Parties summit.

The representatives of more than 190 countries have arrived in Paris for the summit, and will negotiate a new pact to combat climate change over the next two weeks.