What is the meaning of the baseline? climate baseline?

Question

What is the meaning of the baseline? climate baseline?

Answer 1

a baseline is the norm you are comparing information against.  If the normal climate for an area includes a baseline temp of 20C then anything warmer than that is above the baseline.

or it gould be the chalk line drawn from 3rd base to home :)

Answer 2

Climate baseline = past climate history, especially temperature.

A lot of times people don't care about the absolute number, just how it has varied over time.  So in climate change, it is interesting to plot changes in temperature over time, compared to a single baseline value.

The problem with a climate baseline, is that the data are EXTREMELY "noisy", with a lot of jagged up and down lines that have to be averaged and smoothed to see any trend.

So it is very difficult to claim today's climate changes are any different from the past.  The current changes easily fit within the noise of past changes in climate.

Answer 3

The idea of using a baseline is a political concept. Since the climate is in a constant state of change, where you set your baseline depends on what story you want to sell.

Example

If you want to show temperatures have fallen over the last thousand years, you can make your baseline in the middle of the medieval warm period 1000 -1100AD

If you want to show that temperatures have risen over the last 500 years, you can make your baseline in the depths of the little ice age around 1500AD.

so when you hear someone talking baseline with respect to climate, you know that they are trying to sell you a political doctrine rather than explainig a scientific concept.