Ice cores provide direct information about how greenhouse gas concentrations have changed in the past, and they also provide direct evidence that the climate can change abruptly under some circumstances.

Ice cores can tell scientists about temperature, precipitation, atmospheric composition, volcanic activity, and even wind patterns. The thickness of each layer allows scientists to determine how much snow fell in the area during a particular year.

The icy layers also hold particles—aerosols such as dust, ash, pollen, trace elements and sea salts—that were in the atmosphere at that time. These particles remain in the ice thousands of years later, providing physical evidence of past global events, such as major volcanic eruptions.

The main limitation of the ice-core data is that it is effectively a 10-year or longer running average, because air of slightly different ages is mixed together in firn layers – layers of compacted snow that falls in one year and survives unmelted to the following year – before the air is sealed off into bubbles in the …

Abstract. Ice cores are remarkably faithful recorders of past climate, providing multiply duplicated reconstructions with small and quantifiable uncertainties.

800,000 years

An ice age is triggered when summer temperatures in the northern hemisphere fail to rise above freezing for years. This means that winter snowfall doesn’t melt, but instead builds up, compresses and over time starts to compact, or glaciate, into ice sheets.

New University of Melbourne research has revealed that ice ages over the last million years ended when the tilt angle of the Earth’s axis was approaching higher values.

Modern humans almost become extinct; as a result of extreme climate changes, the population may have been reduced to about 10,000 adults of reproductive age. Extinction!

Bacteria have been the very first organisms to live on Earth. They made their appearance 3 billion years ago in the waters of the first oceans.

We know that life began at least 3.5 billion years ago, because that is the age of the oldest rocks with fossil evidence of life on earth. These rocks are rare because subsequent geologic processes have reshaped the surface of our planet, often destroying older rocks while making new ones.

The earliest known life-forms are putative fossilized microorganisms, found in hydrothermal vent precipitates, that may have lived as early as 4.28 Gya (billion years ago), relatively soon after the oceans formed 4.41 Gya, and not long after the formation of the Earth 4.54 Gya.

Bacteria were widespread on Earth at least since the latter part of the Paleoproterozoic, roughly 1.8 billion years ago, when oxygen appeared in the atmosphere as a result of the action of the cyanobacteria. The Bacteria and Archaea diverged from their common precursor very early in this time period.