
The study of past climates
prior to the instrument
record.

Scientists use indirect
evidence (data) during
past time periods to
determine the climate at
that time period.

These climate imprints
are referred to as
proxies.

It may help us to understand natural climate
changes.

The study of past climates may give us
information into future climate scenarios.
Warm
Cold
Warm
Satellites
Historical Proxy Records
Ancient Proxy Records
Instrument
Record

The instrument record extends back about 150
years (~1860).

Since that time Earth’s temperature has increased
0.7 °C (1.3 °F).

In the past, climates were sometimes much colder
than today.

At other times they were much warmer than today.
Tree
Rings
Sediment
Cores
Pollen
Examples
of Climate
Proxies
Stable
Isotopes
Ice Cores
Coral
Reefs

Weather and climate observations can be found in
ships logs, farmers’ diaries, newspaper accounts,
and other written records.

Sediment cores can be taken from lakes,
the shallow ocean, or the deep ocean.

In some cases the thickness of these
layers can be used to infer past climate.

In other cases, these layers are
composed of organic material that can
be analyzed for other climate proxies.

Pollen grains are well
preserved in lake and ocean
sediment.

The analysis of each of these
sediment layers provides
information on the vegetation
present at that time.

Scientists can infer past
climates (warm or cold) based
on the distribution and
changes in plant species.


The most common element used in climate
studies is oxygen.
The isotopes of oxygen are:
◦ O18 (rare)
◦ O17
◦ O16 (common)

The ratio of O18 to O16 is affected by temperature
and can be used as a climate proxy.

Corals are composed of calcium carbonate.

This carbonate contains isotopes of oxygen that
can be used to determine the water temperature
when and where the corals grew.



As snow and ice accumulate in polar glaciers a
paleoclimate record accumulates of the
environmental conditions of the time of
formation.
Ice cores can analyzed using stable isotope
approaches for water or air bubbles within the
ice as a record of past atmospheric
gas concentrations.

Tree growth is influenced by climate. These patterns
can be seen in tree ring width and isotopic
composition.

Trees generally produce one ring each year.

Trees ring records can extend back to the last 1000
years.
All of these examples used individually
or together can help piece together
the past climate of a particular time
period or region.