How is Climate Change Observed and Objectively Measured
How is Climate Change Observed and Objectively Measured?
Objective, reproducible observations and measurements are the
basis of the scientific method: making objective unbiased observations. First
scientists must agree upon a set of parameters to observe that are considered to
be caused by or indicative of climate change. Below are these parameters:
Air and sea temperature: This is the most obvious;
comparing current temperatures to historic ones and looking for
statistically significant trends.
Greenhouse gas levels: it has been established and
generally accepted among scientists that air and sea temperatures rise
as the level of greenhouse gas emissions increases, s up to a maximum.
Snow, glacial and permafrost thickness: As
global temperatures increase, ice and snow will melt; similarly as they
decrease, the size of glaciers and ice packs increases.
and Sea level:
If polar ice and regional glaciers melt, the water eventually makes its
way to the oceans and sea levels rise.
- Ice core samples: As ice forms it traps dust
particles, atmospheric gas and microscopic organisms, all of which
provide clues to changes in the environment over time. And since ice
made of oxygen and hydrogen, we can examine the ratio of oxygen isotopes
in the water, which helps to determine conditions when the ice was
- Lake sediments: Core samples collect through the
bottom of a lake also show us the different isotopes of Oxygen and
Carbon, as well as species of plants and animals that lived in or near
the lake. Since different animals and plants can prefer and tolerate
different temperatures and conditions, this provides clues to the
climate in the past.
- Radiocarbon dating: carbon also has different
isotopes, C12, C14, etc. which reflect changes in the atmosphere. When
this carbon is taken up by living things, such as wood or animals, we
can later compare the ratios of isotopes to the age of the organism.
Indirectly, then , this can be used to look at changes in populations of
organisms over time, which may (or may not) be due to changes in
- Tree rings: Every child knows the thickness of tree
rings tells us abut the tree's seasonal growth, such as thicker rings
(more growth) in a wet, warm year.
Extreme weather events: in some cases climate
change can also be an increase in extreme weather events, for example
hurricanes and storms. However, there is substantial normal variation,
so these must be looked at over a much longer period of time to be
- Animal and plant migration distributions: animals
and plants can migrate over time toward or away from areas that are well
suited toward them, or they can adapt and change to changing conditions.
- Phenology: The timings of natural life cycles, such
as when birds come out of the eggs, to determine if there are changes in
So, the list above are the natural phenomena that scientists examine to
help determine if there is climate change. But remember, there can be other
causes for changes in these parameters other than the climate. So a
scientist must be careful not to draw conclusions too quickly, without
eliminated other possible interactions.
So what data has been collected and what does it show us?