In science, the only thing better than measurements made in the real world are multiple sets of measurements – all pointing to the same answer. That’s what we find with climate change. The case for human caused global warming is based on many independent lines of evidence. Our understanding of climate comes from considering all this evidence. In contrast, global warming skepticism focuses on narrow pieces of the puzzle while neglecting the full picture.

What is the full picture? Humans are emitting around 30 billion tonnes of carbon dioxide into the air every year. This is leaving a distinct human fingerprint:

Signs of warming are found all over the globe (here are just a few):

Ice sheets are melting
Sea levels are rising
Biological changes in tens of thousands of species
Glaciers are retreating
Seasons are shifting
Species are becoming extinct

On the question of human caused global warming, there’s not just a consensus of scientists – there’s a consensus of evidence. In the face of an overwhelming body of evidence, the most common approach of climate skepticism is to focus on narrow pieces of data while neglecting the full picture.

Let's look at an example. One popular skeptic argument has been to cast doubt on the surface temperature record.

Let's look at an example. One popular skeptic argument has been to cast doubt on the surface temperature record. Skeptics claim thermometers are unreliable because surroundings can influence the reading. They reinforce this by showing photo after photo of weather stations positioned near warming influences like air conditioners, barbeques and carparks. The Skeptics Handbook goes so far as to say "the main 'cause' of global warming is air conditioners".

This myopic approach fails to recognise that air conditioners aren't melting the ice sheets. Carparks aren't causing the sea levels to rise and glaciers to retreat. The thousands of biological changes being observed all over the world aren't happening because someone placed a weather station near an air conditioner. When you step back and survey the full array of evidence, you see inescapable evidence of warming happening throughout our planet.

Our understanding of climate doesn't come from a single line of evidence. We use multiple sets of measurements, using independent methods, to further our understanding. Satellites find similar temperature trends to thermometer measurements. This is despite the fact that no carpark or barbeque has ever been found in space. Prominent skeptic Roy Spencer (head of the team that collects the satellite data) concluded about the HadCRUT surface record:
“Frankly our data set agrees with his, so unless we are all making the same mistake we’re not likely to find out anything new from the data anyway"

Our climate is changing and we are a major cause through our emissions of greenhouse gases. Considering all the facts about climate change is essential for us to understand the world around us, and to make informed decisions about the future.