Climate Science - The Basics
Climate Science Part 1
This is the first of a series of blog posts that will give you a basic introduction to the science behind climate change, explain how humans are changing the climate and steer you towards to the latest scientific evidence. Search for the “Climate Science” category on our blog page to find the rest of the series.
What is the difference between climate and weather?
Some of the most common misconceptions about climate change boil down to a fundamental misunderstanding about the difference between climate and weather. The difference is simply one of timescales.
As the UK Met Office explain “weather describes the conditions of the atmosphere over hourly or daily measurements such as temperature, rainfall, cloudiness, sunshine, and wind speeds. Climate, on the other hand, is the average of these conditions over longer time periods ranging from years to decades”.
It’s as simple as that.
What is Climate Change, and is it the same as Global Warming?
Global Warming is a term that refers to the long-term increasing average temperature of the Earth. Climate Change is a broader term that encompasses changes to the Earth’s climate, such as rising sea levels, acidification of the oceans, ice melt, and global temperature increases. Both phrases are often used interchangeably but it is worth knowing they have slightly different definitions.
The changes to the Earth that fall under the term Climate Change are all fundamentally caused by an increase in the global temperature, so what is actually making the Earth warmer? While the Earth’s climate has changed over time, the scientific consensus is that humans have caused, and are causing, significant and rapid warming through the production of large amounts of Greenhouse Gas emissions (GHGs). These gases can cause warming via a process known as the Greenhouse Effect. We will cover the full extent of the scientific consensus and what that really means in a future blog.
What is the Greenhouse Effect?
Each day the Earth is bombarded with solar radiation from the Sun, in the form of visible light, as well as radiation across the electromagnetic spectrum such as ultraviolet (UV) and infrared (IR) light. Roughly 30% of this radiation is reflected back into space by clouds and other bright surfaces such as ice. 70% is absorbed by the Earth’s oceans and land. This delicate balance of reflection and absorption is what keeps the Earth’s climate at the right temperature to allow life to flourish.
Around the Earth a “blanket” of gases such as CO2, methane and water vapour help balance the system. These so-called greenhouse gases allow incoming UV radiation from the sun to pass through them on its way to the surface of the Earth because of its shorter wavelength. However, when that radiation heats up the land and seas it is re-emitted as heat (infra-red radiation) back out to the atmosphere it has a longer wavelength. The longer wavelength radiation is then absorbed by the GHGs and re-emitted in all directions. The result of this is that some heat is “trapped” under the blanket, heating the Earth and causing the greenhouse effect, as shown below.
It may be surprising to hear that the greenhouse effect is actually very beneficial to Earth. Without it the planet could be as cold as the Moon and very inhospitable to life, but the blanket can become too effective if too many GHGs are emitted into the atmosphere, heating the Earth beyond its natural balance point. This is what is happening now, and has been since humans began producing greenhouse gases on an industrial scale, the blanket is becoming too strong and the earth has warmed 1°C as a result (see below).
Image courtesy of NASA Goddard Institute for Space Studies - Global Annual Mean Surface Air Temperature Change. Land-ocean temperature index, 1880 to present, with base period 1951-1980. The solid black line is the global annual mean and the solid red line is the five-year lowess smooth.
GISTEMP Team, 2020: GISS Surface Temperature Analysis (GISTEMP), version 4. NASA Goddard Institute for Space Studies. Dataset accessed 03-08-2020 at https://data.giss.nasa.gov/gistemp/.
Some very good introductions to climate science from the most reputable sources can be found here:
The rest of this series will explain how humans have influenced the climate and show how the climate can correct itself via feedback loops. We will also give an overview of the history of Earth’s climate, share various predictions for the future, and examine the key question of scientific consensus - so follow our blog to find out more!