Are people natural or made by people

Natural or Man Made?

In addition to the measurements, the criticism of the climate skeptics mainly focuses on the interpretation of the data and models. The focus here is on the causes and connections of climate development. Here is a small selection of the most common arguments and objections:

Natural fluctuations

Objection:

The earth's climate has experienced strong temperature fluctuations over and over again in the course of the earth's history. Today's temperature rise is nothing more than a tiny section of a long chain of natural ups and downs. A connection between climate and human influences is therefore neither demonstrable nor necessary to explain the changes.

Reply:

There is broad consensus that current warming is likely to have both natural and anthropogenic causes. However, while in the first half of the 20th century natural influences such as fluctuations in solar radiation seem to have predominated, in the second half everything points to an increasing anthropogenic influence. If one compares the values ​​modeled for the last century with the actually observed values, the scenario with both natural and anthropogenic factors fits best to reality.

Solar cycle as the cause

Objection:

It is not the greenhouse gases but above all the fluctuations in solar radiation due to changes in solar activity that are responsible for climate fluctuations. Above all, the 11-year cycle of activity and sunspots has an impact. Periods such as the “Little Ice Age” between 1500 and 1800, when temperatures dropped significantly in Europe, prove this.

Reply:

New studies, including by NASA, indicate that the effects of fluctuations in solar activity on the global climate are only minor. According to the IPCC, the proportion of warming caused by solar influences from 1750 to 2000 can be set at around 0.3 watts per square meter - less than a tenth of the probable CO2-related warming. However, the uncertainty factor for assessing the effects of the sun is at least 67 percent.

The studies also show, however, that the solar cycle has a greater influence on the energy flows and distribution in the atmosphere and can thus trigger significant climatic effects not globally, but regionally. This could also explain the “little ice age”, because both this and the medieval warm period that preceded it can only be identified as regional, not global, phenomena using ice cores from glaciers and ice caps.

In its discussion of the solar factors, the IPCC notes that the understanding of solar processes and their climatic influences is still “very poor”. For example, the fluctuations in solar radiation determined in different studies over the past four hundred years differ greatly from one another, among other things because they are difficult to determine in retrospect.


Status: 04/20/2002

April 20, 2002