About global warming, a letter this past Monday said "scientists never say how much is caused by humankind versus mother nature." Actually, they do say. One good reference is the Bloomberg web article "What's Really Warming the World." It shows the separate effects of earth orbit and solar variations, volcanoes (which tend to cool), deforestation, ozone, and aerosols (another cooler). Temperature does not rise as fast as from CO2 alone, but from the combination, and CO2 is the largest contributor.
The web has several "refutations" of Bloomberg, starting out with insulting words like "absurd," "fanatics," and "notoriously unreliable." Reminds me of when a debate coach told me, "If you can't win an argument, criticize your opponent."
Actually, the Bloomberg article is conservative, as it does not mention warming from CO2 released from thawing permafrost, or methane (an even stronger greenhouse gas) released from ocean-floor hydrates..
Let me comment on the old claim that "only" 97 percent of scientists' articles support global warming. That included scientists from other fields than climate. Recently, a survey reviewed the papers by those actually working with climate. All but 2 of 10,885 scientific articles agree that warming is happening and we are to blame.
John F. Moore