This information comes from NASA’s website. You’ll find interesting presentations of scientific data by visiting it at http://climate.nasa.gov/index

While summer temperatures have been blistering in both hemispheres, this video takes the longer historical view. It comes to us from our friends at NASA and is an amazing 26-second animation depicting how temperatures around the globe have warmed since 1880. That year is what scientists call the beginning of the “modern record.”

You’ll note an acceleration of those temperatures in the late 1970s as greenhouse gas emissions from energy production increased worldwide and clean air laws reduced emissions of pollutants that had a cooling effect on the climate, and thus were masking some of the global warming signal.

The data come from NASA's Goddard Institute for Space Studies in New York, which monitors global surface temperatures.

Changes in Earth’s climate

The Earth's climate has changed throughout history. Just in the last 650,000 years there have been seven cycles of glacial advance and retreat, with the abrupt end of the last ice age about 7,000 years ago marking the beginning of the modern climate era — and of human civilisation. Most of these climate changes are attributed to very small variations in Earth’s orbit that change the amount of solar energy our planet receives.

The current warming trend is of particular significance because most of it is very likely human-induced and proceeding at a rate that is unprecedented in the past 1,300 years.

Earth-orbiting satellites and other technological advances have enabled scientists to see the big picture, collecting many different types of information about our planet and its climate on a global scale. Studying these climate data collected over many years reveals the signals of a changing climate.

The evidence for rapid climate change is compelling:

Glacial retreat

Glaciers are retreating almost everywhere around the world – including in the Alps, Himalayas, Andes, Rockies, Alaska and Africa.

Shrinking ice sheets

The Greenland and Antarctic ice sheets have decreased in mass. Data from NASA's Gravity Recovery and Climate Experiment show Greenland lost 150 to 250 cubic kilometres (36 to 60 cubic miles) of ice per year between 2002 and 2006, while Antarctica lost about 152 cubic kilometres (36 cubic miles) of ice between 2002 and 2005. Current data show that this trend is continuing.

Declining Arctic sea ice

Both the extent and thickness of Arctic sea ice has declined rapidly over the last several decades at a rate of 11.5% per decade.

Sea level rise

Global sea level rose about 17 centimetres (6.7 inches) in the last century. The rate in the last decade, however, is nearly double that of the last century and is due to two factors: added water coming from melting land ice and the expansion of sea water as it warms.

Global temperature rise

All three major global surface temperature reconstructions show that Earth has warmed since 1880. Most of this warming has occurred since the 1970s, with the 20 warmest years having occurred since 1981 and with all 10 of the warmest years occurring in the past 12 years. Even though the 2000s witnessed a solar output decline resulting in an unusually deep solar minimum in 2007-2009, surface temperatures continue to increase.

Warming oceans

The oceans have absorbed much of this increased heat, with the top 700 metres (about 2,300 feet) of ocean showing warming of 0.302 degrees Fahrenheit since 1969.

Ocean acidification

Since the beginning of the Industrial Revolution, the acidity of surface ocean waters has increased by about 30 percent. This increase is the result of humans emitting more carbon dioxide into the atmosphere and hence more being absorbed into the oceans. The amount of carbon dioxide absorbed by the upper layer of the oceans is increasing by about 2 billion tons per year.

Extreme events

The number of record high temperature events in the United States has been increasing, while the number of record low temperature events has been decreasing, since 1950. The U.S. has also witnessed increasing numbers of intense rainfall events. This pattern is repeated in other countries with a higher incidence of super-typhoons, fires, drought and floods.

The role of human activity

In its recently released Fourth Assessment Report, the Intergovernmental Panel on Climate Change, a group of 1,300 independent scientific experts from countries all over the world under the auspices of the United Nations, concluded there is a more than 90 percent probability that human activities over the past 250 years have warmed our planet.

The industrial activities that our modern civilisation depends upon have raised atmospheric carbon dioxide levels from 280 parts per million to 379 parts per million in the last 150 years. The panel also concluded there is a better than 90 percent probability that human-produced greenhouse gases such as carbon dioxide, methane and nitrous oxide have caused much of the observed increase in Earth's temperatures over the past 50 years.

They said the rate of increase in global warming due to these gases is very likely to be unprecedented within the past 10,000 years or more. The panel's full Summary for Policymakers report is online at http://www.ipcc.ch/pdf/assessment-report/ar4/syr/ar4_syr_spm.pdf

Solar irradiance

It's reasonable to assume that changes in the sun's energy output would cause the climate to change, since the sun is the fundamental source of energy that drives our climate system.

Indeed, studies show that solar variability has played a role in past climate changes. For example, a decrease in solar activity is thought to have triggered the Little Ice Age between approximately 1650 and 1850, when Greenland was largely cut off by ice from 1410 to the 1720s and glaciers advanced in the Alps.

But several lines of evidence show that current global warming cannot be explained by changes in energy from the sun:

·         Since 1750, the average amount of energy coming from the Sun either remained constant or increased slightly.

·         If the warming were caused by a more active sun, then scientists would expect to see warmer temperatures in all layers of the atmosphere. Instead, they have observed a cooling in the upper atmosphere, and a warming at the surface and in the lower parts of the atmosphere. That's because greenhouse gasses are trapping heat in the lower atmosphere.

·         Climate models that include solar irradiance changes can’t reproduce the observed temperature trend over the past century or more without including a rise in greenhouse gases.

The challenge of adapting to future climate

Our lives and livelihoods are shaped by the climate, so adapting to future climates will involve nearly all aspects of our economies, societies and the environment. Our ingenuity will help us find technological solutions to reducing greenhouse gases but we will also need to ask some deep questions in terms of our relationship with the environment and make some difficult personal and social choices.