Interesting discovery. Apparently no one can accurately estimate the global assets of the Catholic Church, not even the Church itself. Most of the assets/income outside of the Vatican are held by the individual dioceses and religious orders for their own use. They're all separate corporations, most led by bishops. Only a small amount (Peter's Pence) is transferred to the Vatican, which has revenue in the low hundreds of millions, mostly from investment returns and tourism. Many of the assets have never been appraised, because the Church would never sell them (e.g., cathedrals, Vatican artwork from the Middle Ages, etc.). Most are on the books for $1.
One figure puts total Catholic Church spending in the U.S. at $170B annually, but most of that money comes from health insurers who pay Catholic hospitals for covered medical procedures, so it's not exactly charity. University tuition received from students is another big part of that total. The biggest Catholic charity in the U.S. spends about $4B annually. Another interesting number is Church collections. The average weekly donation in the U.S. is $10, although the source wasn't clear if that was per Catholic or per family. That totals at most $36B. That's not even enough for disaster recovery from one major hurricane.
In Germany, church members are actually taxed by the federal government on behalf of the churches, which then get the money. Try that in the U.S. :-)
It's going to be tricky imagining a Catholic Church rich enough to lead much of the world's response to accelerating climate change. I need a Church that grows exponentially 3-4 decades from now as people afraid of the end times return to God, and to the Catholic Church in particular. I was hoping for up to 2B Catholics by the start of the book, which is about 50% more than the current figure. On the up side, 30-40 years is more than enough time to build big companies like Apple, Facebook, or Google. If the Church could build or inherit that kind of wealth, it could make quite a dent and attract more followers.
I could do the story with current numbers, although the Book of Revelation prophecies a worldwide religion, so it would be better if the Church was much larger to justify it becoming the Antichrist's main target.