Ok, I have to get this off my chest. It's a long-winded rant, but so be it.
The environment is like most issues: there is a reasonable middle ground. Unfortunately everyone appears to have an extreme position on this issue, one side or the other. Both extremes are wrong!
I looked at data; based on data from Vostok ice cores, the global temperature increased slowly but steadily for 300 years before the beginning of the industrial revolution. Starting the beginning of the industrial revolution in 1855, the global temperature dropped. There were spikes of global warming during World War 1 & 2, but other than that it dropped until 1970. During the 1960s and 1970s, scientists were worried we were seeing the beginning of the next ice age. The sampled ice cores in Greenland and found the last ice age showed normal temperatures, then dropped to full ice age over a period of only 10 years. That's within a single person's lifespan. So they were worried the next ice age was about to trigger. They seriously suggested dropping big thermonuclear bombs on polar ice caps, to melt the ice. Others objected, pointing out how much radiation that would release. While scientists were worried how to stop global cooling, one scientist published a paper in 1979 that talked about global warming. Other scientists said "Are you nuts? We just spent 2 decades talking about global cooling, and you claim global warming?" But he published his data long with his paper. Scientists examined his data, double checked it, triple checked, and started collecting new data. All the data confirmed his findings. Since 1970 (just 9 years before his paper) the planet has been undergoing global warming.
Al Gore went on his tour with his hockey-stick graph. It showed steady global warming from 1970, then some time in the 1990s a sharp increase in the rate. That data was later shown to be falsified. But the steady global warming from 1970 was confirmed. In fact, later there was a sharp reduction in the rate of global warming. Since year 2000 global warming slowed down. It didn't stop, just slow. If you take the data from 1550 to 1855, and project that trend into the future, it equals the temperature it actually was in year 2000. So that means the planet underwent rapid global warming during the last 3 decades of the 20th century. Not as fast as Al Gore claimed, but relatively rapid. Once the temperature equalled what it would have been due to nature, then global warming slowed. It's still faster than nature, but slower than what it was. Why?
The industrial revolution was based on coal. They spewed coal smoke and soot into the air. Cities were dirty with coal. Even homes were heated with it. People living near factories complained about the soot, so factories built smoke stacks higher. This just moved the soot farther from the factory. So factories built smoke stacks higher. Eventually they hired engineers to design smoke stakes to create an up-draft that drew smoke and soot into the clouds. This left the soot so far down wind that no one could trace it to where it came from. But eventually factories and coal fired generating stations were required to stop this. They had to put scrubbers in place. There is still arguments about sulphur dioxide, which combines with water in clouds and UV from sunlight to form sulphuric acid. When that rains, it's acid rain. But my assertion is those smoke stacks that produced up-drafts blew smoke into the stratosphere. It takes years for that to settle out. Well, it did. By year 2000, all the soot and smoke had settled out, and the planet recovered.
All this shows humans have had profound impact on the environment. But most climate warriors chose to ignore the century of global cooling: 1855 to 1970. Anyone with a brain can see the goal is not to return to the artificially frigid 1960s. That was *AFTER* a century of global cooling caused by humans. In fact my mother told me of picnics her parents took the family on when she was a child. Picnics in a meadow that used to be the middle of a lake where her uncle used to fish. The lake had dried up. Today, southern Manitoba is much wetter than it was. Jacob's Lake is back, although people who live there now don't know it used to be there.
Another fact: the bottom of the ocean is literally ice cold, even at the equator. Think about that. Volcanoes show us what's below our feet. At the equator, surface water is warm tropical water. Below the ocean crust is red hot magma. There is miles of rock between the magma and ocean water, but rock isn't a good insulator, and any insulator just slows heat transfer, it doesn't stop it. So ice water at the bottom of the ocean, trapped between warm tropical water and red hot magma. What keeps it cold? The answer is nothing. It doesn't stay cold, it's warming up. Paleontologists found the ocean was warm all the way to the bottom at the time of the dinosaurs. That's what we're heading to today. The planet is still slowly warming out of the last ice age. When you put a kettle on for a pot of tea, or a pot of water to make spaghetti, it takes a long time to boil. Now imagine how long it takes to warm an entire ocean. That's what's happening. From the plant's perspective, we are not long out of the last ice age. We are still warming.
Minor ice ages (glacial periods) occur every 100,000 to 125,000 years. The last minor one ended just thousands of year ago. To quote Wikipedia:
$1:
The major glacial stages of the current ice age in North America are the Illinoian, Sangamonian and Wisconsin stages. The use of the Nebraskan, Afton, Kansan, and Yarmouthian (Yarmouth) stages to subdivide the ice age in North America have been discontinued by Quaternary geologists and geomorphologists. These stages have all been merged into the Pre-Illinoian Stage in the 1980s.
During the most recent North American glaciation, during the latter part of the Wisconsin Stage (26,000 to 13,300 years ago), ice sheets extended to about 45 degrees north latitude. These sheets were 3 to 4 km thick.
And some people wonder why our planet is still warming?
Another major complication is deep ocean currents. Scientists estimate it takes 1,000 years to complete one full circuit of the globe. The fact the number is so round tells me it's a very rough estimate. This current helps explain why deep ocean water is cold, at least in the Pacific. When Antarctica has winter, ice shelves grow. During southern winter (our summer) some of that ice sublimates in dry arctic wind. That leaves salt behind in the ice. In spring that extra salty ice melts, producing a heavy fall of ice cold brine. That brine is heavier that ocean water, it falls to the ocean floor. This does account for the ice water somewhat, but when dinosaurs roamed the Earth during the last major interglacial period, the north pole melted completely every summer, and Antarctica had a taiga forest. That means forest growing on permafrost, like Alaska or Yukon or Northwest territories today.
And the Sahara desert grows during every interglacial period. Even during periods between minor ice ages, the Sahara grows to an extent much larger than it is today.
All this says yes, humans do have profound impact on the environment. But the goal is not to return to the artificially frigid 1960s. The goal is not to pick a temperature and stop global warming there. You can't. For one thing the deep ocean currents have 1,000 years of momentum. Trying to stop that is like stopping a train with your bare hands. You can't. But we can slow global warming to the natural rate. Slowing it will do a few things. We can stop growth of the Sahara, perhaps even turning edges of the desert into Sahel. And places that do experience flooding will do so slowly. If a young couple buys a home in New Orleans as soon as they graduate from college or university, then the area experiences flooding when they are senior citizens who have to move to a nursing home. Then don't sell the house, instead return the land to nature. Flooding at that rate will not affect them.
Slowing the rate of global warming is a lot easier. And it means we don't need extreme measures like cap-and-trade or carbon tax. We do need subsidies for green technology. And ensure other levels of government do not undo those subsidies.