The quick answer is yes it is: Earth is already showing many signs of worldwide climate change. What's more; the rate of this warming is increasing: climate studies have shown that the last two decades of the twentieth century were the hottest in the last 400 years and possibly for several millennia.
Most scientists now relate this accelerated warming to the presence of additional "greenhouse" gases trapping extra energy within the atmospheric system, with people's activities such as burning coal, oil and gas leading to an escalation in these greenhouse gases.
So what's the problem?
The effects of climate change pose an unprecedented threat to our planet. Flooding, coastal erosion, droughts, salt water intrusion into soils, high levels of tropical storms, cyclones, and large amounts of rainfall are among the effects already attributed to global warming over past years. With some forecasts predicting a temperature rise of between 1.8 and 4 degrees Celsius by the end of this century, these problems will only get worse. The severe climate effects caused by global warming will have a catastrophic effect on our planet, causing unprecedented rates of death and disease. A report by the Intergovernmental Panel on Climate Change (IPCC) has warned that if global warming is left unchecked it could "extinguish hundreds of millions of lives and nearly a third of the planet's wildlife."
It's time for action
In short, something has to be done quickly about climate change. We owe it to ourselves and to future generations to take action now to make positive changes to counteract our negative impact on the environment and to make the world a cleaner, healthier place.