Five charts that prove this selloff is serious

Stock markets around the world seem to be already in confirmed selloff territory or very close to it.

Here, we take a look at some key charts which demonstrate why this pessimistic mood looks set to continue.

Was this where it all began? China's benchmark index is one of the worst-hit of the major global equity markets. While the roots of the current selloff may be deep, much of the pile-in panic seems to have been sparked by fears that China's economy, the second-largest in the world, is not going to deliver the growth figures once hoped for.

The Chinese central bank's devaluation of the yuan earlier this month, as it suggested that the country needed to boost its exports, caused some of the more serious concerns to crystallize. While it was aimed at stabilization, the performance of the country's main stock market index since then suggests this has not yet been achieved.

This chart illustrates how other major currencies are weighted against the U.S. dollar – and can be used as a forward indicator of U.S. trade with other countries.

The slump in other currencies against the U.S. dollar is motivated both by fears of a currency war, where countries become locked in a competition to devalue their currencies in an effort to boost exports, and about whether the U.S. Federal Reserve will start raising interest rates in September, as many expected.

As owning an iPhone or iPad has become a sign of affluence, Apple shares have become the benchmark not only for the technology sector, but also for confidence in the global economy.

The technology giant's size is regularly talked of breathlessly and compared to the gross domestic product of small countries. The plunge in its share price last week didn't follow a product warning or other scare – it appears to be mainly a crisis of confidence that people around the world, particularly in China, will continue buying yet more upgrades of the company's pricey -- but pretty -- products.

Gulp. The price of oil is vulnerable to many different factors, lots of them complicated geopolitical issues like the conflict in the Middle East or Ukraine. The recent selloff appears to be motivated by the most over-arching of all: concerns about the global economy – and particularly China -- not growing as fast as expected, and therefore needing less oil.

There was a huge spike in market volatility, as measured by the VIX index, last week. August is now on track to be the most volatile month for equity markets in 25 years – more volatile than after apparently sciesmic events like the collapse of Lehman Brothers or the bursting of the tech stocks bubble.

What's behind this? Partly it's that August is a relatively low-volume month, with plenty of traders away from their desk. But perhaps more importantly, it's the atmosphere of fear and panic about a number of factors: China's economy; currency wars and the price of oil among them.

- By CNBC's Catherine Boyle