Yes, the vast majority of actively publishing climate scientists agree that humans are causing global warming and climate change. A number of so-called ‘consensus’ studies analysed published articles on climate change and found an overwhelming agreement on human-caused global warming. Depending on the methodology used, they come to the conclusion that between 91% and 100% of scientists agree that climate change is happening and humans are responsible. Read more on studies conducted between 2004 and 2015 here and the latest study from 2017 here.

The greenhouse effect is the way in which heat is trapped close to the surface of the Earth by “greenhouse gases.” These heat-trapping gases can be thought of as a blanket wrapped around the Earth, which keeps it toastier than it would be without them. Greenhouse gases include carbon dioxide, methane and nitrous oxides.

Greenhouse gases arise naturally, and are part of the make-up of our atmosphere. Earth is sometimes called the “Goldilocks” planet – it’s not too hot, not too cold, and the conditions are just right to allow life, including us, to flourish. Part of what makes Earth so amenable is the naturally-arising greenhouse effect, which keeps the planet at a friendly 15 °C (59 °F) on average. But in the last century or so, humans have been interfering with the energy balance of the planet, mainly through the burning of fossil fuels that give off additional carbon dioxide into the air. The level of carbon dioxide in Earth’s atmosphere has been rising consistently for decades and traps extra heat near the surface of the Earth, causing temperatures to rise.

Source: NASA

Ice cores are scientists’ best source for historical climate data. Other tools for learning about Earth’s ancient atmosphere include growth rings in trees, which keep a rough record of each growing season’s temperature, moisture and cloudiness going back about 2,000 years. Corals also form growth rings that provide information about temperature and nutrients in the tropical ocean. Other proxies, such as benthic cores, extend our knowledge of past climate back about a billion years into the past. Read more here.

Three of the world’s most complete temperature tracking records – from NASA’s Goddard Institute for Space Studies, the National Oceanic and Atmospheric Administration’s National Climactic Data Center and the UK Meteorological Office’s Hadley Centre – begin in 1880. Prior to 1880, temperature measurements were made with instruments like thermometers. The oldest continuous temperature record is the Central England Temperature Data Series, which began in 1659, and the Hadley Centre has some measurements beginning in 1850, but there are too few data before 1880 for scientists to estimate average temperatures for the entire planet. Data from earlier years is reconstructed from proxy records like tree rings, pollen counts and ice cores. Because these are different kinds of data, scientists generally don’t put proxy-based estimates on the same charts as the “instrumental record.”

The above-mentioned agencies and others collect temperature data from thousands of weather stations worldwide, including over the ocean, in Antarctica and from satellites. However, instruments are not perfectly distributed around the globe, and some measurement sites have been deforested or urbanized since 1880, affecting temperatures nearby. Each agency uses algorithms to filter the effects of these changes out of the temperature record and interpolate where data is sparse, like over the vast southern ocean, when calculating global averages. Generally, all three datasets agree quite closely (see graph above) and are in agreement on the trend of global warming since the Industrial Revolution.

Source: NASA

Overall, volcanoes release less than 2 percent of the equivalent amount of CO2 released by human activities. Quite small. However, about once every 20 years there is a volcanic eruption (e.g., Mount Pinatubo, El Chichon) that throws out a tremendous amount of particles and other gases. These will effectively shield us enough from the Sun to lead to a period of global cooling. The particles and gases typically dissipate after about 2 years, but the effect is nearly global.

Source: NASA