function CO2ticker()
{
//get current time
var today=new Date();

//create variables with most recent CO2 measurement and current growth rate
var CO2fix = 388.32;
var growth = 0.0056016427104723;

//create a variable with the time and date of most recent measurement
var fixDate=new Date();
	fixDate.setFullYear(2010,6-1,15);
	fixDate.setHours (0);
	fixDate.setMinutes(0);
	fixDate.setSeconds(0);
	fixDate.setMilliseconds(0);

//work out time elapsed since most recent measurement, in days rather than milliseconds
var elapsed = (today.getTime()-fixDate.getTime())/(1000*60*60*24);

//calculate current concentration based on last fix, growth rate and elapsed time
var currentCO2= CO2fix+(growth*elapsed);

//write the values to the appropriate parts of the html document
if (document.getElementById('current_co2'))
	{
	document.getElementById('current_co2').innerHTML=currentCO2.toFixed(CO2Precision);
	}

if (document.getElementById('growth_rate'))
	{
	document.getElementById('growth_rate').innerHTML=growth.toFixed(GrowthRatePrecision)
	}

if (document.getElementById('elapsed'))
	{
	document.getElementById('elapsed').innerHTML=elapsed.toFixed(ElapsedTimePrecision)
	}

if (document.getElementById('last_measurement_date'))
	{
	document.getElementById('last_measurement_date').innerHTML=fixDate;
	}

if (document.getElementById('last_measurement_co2'))
	{
	document.getElementById('last_measurement_co2').innerHTML=CO2fix;
	}

//set how often the values are refreshed (in milliseconds)
t=setTimeout('CO2ticker()',RefreshRate);
}