Primer: What is Climate Change?

American Samoa. Credit: The Ocean Agency/XL Catlin Seaview Survey.

This primer is written for the non-scientific community in the Pacific and for those new to an understanding of what ' climate change' is, and what it means for the people of the Pacific.

For newcomers to the science, it's important to highlight that in order to understand climate change  - on Planet Earth, in the Pacific region, anywhere in the world - you first need to know the distinction between 'climate' and 'weather'.


The generally accepted distinction is based on time periods.


Weather

How the sun, rain, wind, temperature outside in the atmosphere behave daily and on any given week.  It could be hot one day, raining the next, or windy and cold another day or all in the same day. Weather can change in a matter of hours or days, even in one season.


Climate

How it behaves over longer time periods. It refers to a region, city or country's usual weather patterns during seasons and longer periods such as centuries and so forth. Earth's climate is a calculation of all the world's climates and refers to the average  of all the world's regional climates.




Climate Change

 

Refers to a change in the usual or average weather of a region or city or country. This could be a change in the average temperature or average rainfall in a given season or month. Simply put, climate change is also a change in Earth's climate. For example it could mean a change in seasons producing hot weather during a winter season, that's a change in that region's usual climate. The timescales for climate change are much longer than weather conditions. And sometimes, you do not see the effects of it immediately.

 

The Relentless Rise of Carbon Dioxide

Source: NASA

Credit: Data - National Oceanic and Atmospheric Administration. Some description adapted from the Scripps CO2 Program website, "Keeling Curve Lessons."

 

NASA explains the rise of carbon dioxide:

Ancient air bubbles trapped in ice enable us to step back in time and see what Earth's atmosphere, and climate, were like in the distant past.

They tell us that levels of carbon dioxide (CO2) in the atmosphere are higher than they have been at any time in the past 400,000 years.

During ice ages, CO2 levels were around 200 parts per million (ppm), and during the warmer interglacial periods, they hovered around 280 ppm (see fluctuations in the graph).

In 2013, CO2 levels surpassed 400 ppm for the first time in recorded history.

This recent relentless rise in CO2 shows a remarkably constant relationship with fossil-fuel burning, and can be well accounted for based on the simple premise that about 60 percent of fossil-fuel emissions stay in the air.

Today, we stand on the threshold of a new geologic era, which some term the "Anthropocene", one where the climate is very different to the one our ancestors knew.

If fossil-fuel burning continues at a business-as-usual rate, such that humanity exhausts the reserves over the next few centuries, CO2 will continue to rise to levels of order of 1500 ppm.

The atmosphere would then not return to pre-industrial levels even tens of thousands of years into the future.

This graph not only conveys the scientific measurements, but it also underscores the fact that humans have a great capacity to change the climate and planet.

Credit: NASA Climate 365 project - a collaboration of the NASA Earth Science News Team, NASA Goddard and Jet Propulsion Laboratory communications teams, and NASA websites Earth Observatory and Global Climate Change.

NASA:

Each year, four international science institutions compile temperature data from thousands of stations around the world and make independent judgments about whether the year was warmer or cooler than average.

“The official records vary slightly because of subtle differences in the way we analyze the data,” said Reto Ruedy, climate scientist at NASA’s Goddard Institute for Space Studies. “But they also agree extraordinarily well.”

All four records show peaks and valleys in sync with each other. All show rapid warming in the past few decades.

All show the last decade has been the warmest on record.

So how warm is Planet Earth?

Earth’s global surface temperatures in 2017 were the second warmest since modern recordkeeping began in 1880, according to an analysis by NASA.

Continuing the planet’s long-term warming trend, globally averaged temperatures in 2017 were 1.62 degrees Fahrenheit (0.90 degrees Celsius) warmer than the 1951 to 1980 mean, according to scientists at NASA’s Goddard Institute for Space Studies (GISS) in New York. That is second only to global temperatures in 2016. Last year was the third consecutive year in which temperatures were more than 1.8 degrees Fahrenheit (1 degree Celsius) above late nineteenth-century levels.

This video shows the data visually. Look at the top right hand side of the screen to see the time period.

Credit

NASA's Scientific Visualization Studio. Data provided by Robert B. Schmunk (NASA/GSFC GISS).

NASA’s temperature analyses incorporate surface temperature measurements from 6,300 weather stations, ship- and buoy-based observations of sea surface temperatures, and temperature measurements from Antarctic research stations.

These raw measurements are analyzed using an algorithm that considers the varied spacing of temperature stations around the globe and urban heating effects that could skew the conclusions.

These calculations produce the global average temperature deviations from the baseline period of 1951 to 1980.

The full 2017 surface temperature data set and the complete methodology used to make the temperature calculation are available at http://data.giss.nasa.gov/gistemp/.

GISS is a laboratory within the Earth Sciences Division of NASA’s Goddard Space Flight Center in Greenbelt, Maryland. The laboratory is affiliated with Columbia University’s Earth Institute and School of Engineering and Applied Science in New York.

NASA uses the unique vantage point of space to better understand Earth as an interconnected system. The agency also uses airborne and ground-based monitoring, and develops new ways to observe and study Earth with long-term data records and computer analysis tools to better see how our planet is changing. NASA shares this knowledge with the global community and works with institutions in the United States and around the world that contribute to understanding and protecting our home planet.

Source: NASA