One example: raise the temperature, and you get more water vapor. More water vapor yields more clouds, which have a *massive* cooling effect. In short: it is entirely possible that CO2 has a negligible effect on the temperature.
Some clouds warm and some cool. Clouds are complicated.
Set the temperature question aside for a moment: is a higher CO2 level a bad thing? CO2's primary effect on the planet is "plant food". Commercial greenhouses deliberately increase CO2 in order to increase their crop yields. If we could magically reduce CO2 to 19th century levels, we would see crop yields fall substantially.
You're forgetting that plants need water, nutrients and light as well. Not enough water? Extra CO2 makes no difference. And so on.
Back to temperature. If the earth's temperature does rise, is this a bad thing? Historically, warmer periods have been times of prosperity. Most of the earth is in the temperate zone, and warmer temperatures improve the climate, lengthen growing seasons, etc. Imagine frozen Siberia as the bread basket of Asia. It is not clear that a warmer earth is bad.
Warming temperatures means that the distribution of temperatures is shifting higher. If the width of the distribution doesn't change at all it will mean more extreme temperatures and therefore more stress on people and places. If the width also changes, say it gets wider, we could have more cold events and more even warmer events.
Finally, how do we measure the temperature of the earth? There are many temperature stations scattered about, but the majority of them do not comply with the guidelines set up to ensure accurate measurement. Many are at airports (lots of tarmac), others - especially in very cold climates - are placed conveniently near buildings. These and other siting issues make the temperature measurements inaccurate. Satellite measurements have their own difficulties. The more you read about these issues, the clearer it becomes that we do not currently have reliable temperature measurements.
This is baloney. Instruments work fine. Collectively, and processed thoughtfully and methodically, the data sets from historical and current instruments is, on the whole, extremely reliable and damning. The Earth is warming. Ocean based instruments confirm it. Atmospheric instruments confirm it. Tree rings confirm it. Radio isotopes confirm it. Seriously, the data is consistent across a wide variety of disciplines.
So: on the basis of inaccurate temperature data and ineffective models, what should we do? Should we commit trillions of dollars to drastic policies based on questionable science? Or should we, maybe, invest in a decent network of weather stations, invest in climate science, and *understand* what is going on?
We have done this and are continuing to do this.
Climate is complex, and the one thing certain about all of the climate models developed to date is that they fail to model climate. If a model is to be useful, it must make falsifiable predictions of future events. To date, no model has done better than a random-number generator. Tropical storms were supposed to increase, but did not. Sea level was supposed to rise faster that ever. In fact, the sea level has been rising steadily since the last ice age,, but the rise has actually slowed in recent times. If one thing is clear, it is that our understanding of climate is woefully inadequate.
Do you actually know anything about this? What do you suppose climate models model? Models are complex and computing resources are limited. Models are doing a great job of simulating changes in climate since the industrial revolution. Really. Forecasting is difficult work. Obviously we can't tell precisely what the future climate will look like until we are there looking back at the record.
