I agree, there is no single 'official' scientific scale for happiness. But there are plenty of calibrated scales out there which are used and utilised for varying specific and scientific needs. Using a common example how do you think clinical depression is diagnosed? Like in your example "one...
The subjective well-being scores are even worse. England 33rd out of 39 countries for life-satisfaction. Overall subjective satisfaction is 30th out of 39. By way of contrast Germany is 11th out of 39. Macedonian kids are the happiest.